1796 lines
186 KiB
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1796 lines
186 KiB
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GitHub
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<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 448 512"><!--! Font Awesome Free 6.1.2 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2022 Fonticons, Inc.--><path d="M439.55 236.05 244 40.45a28.87 28.87 0 0 0-40.81 0l-40.66 40.63 51.52 51.52c27.06-9.14 52.68 16.77 43.39 43.68l49.66 49.66c34.23-11.8 61.18 31 35.47 56.69-26.49 26.49-70.21-2.87-56-37.34L240.22 199v121.85c25.3 12.54 22.26 41.85 9.08 55a34.34 34.34 0 0 1-48.55 0c-17.57-17.6-11.07-46.91 11.25-56v-123c-20.8-8.51-24.6-30.74-18.64-45L142.57 101 8.45 235.14a28.86 28.86 0 0 0 0 40.81l195.61 195.6a28.86 28.86 0 0 0 40.8 0l194.69-194.69a28.86 28.86 0 0 0 0-40.81z"/></svg>
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Crashkurs Java im Modul Algorithmen und Datenstrukturen
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</a>
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</li>
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01: Hello World
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02: Basics
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03: Coding Style
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04: Einführung in Objekte
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<li class="md-nav__item">
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05: Typen von Objekten
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<a href="06_java_docs.html" class="md-nav__link">
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06: JavaDoc
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</a>
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<label class="md-nav__link md-nav__link--active" for="__toc">
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Print as PDF
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<span class="md-nav__icon md-icon"></span>
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</label>
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<a href="print_page.html" class="md-nav__link md-nav__link--active">
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Print as PDF
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</a>
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Inhaltsverzeichnis
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<li class="md-nav__item">
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<a href="#" class="md-nav__link">
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1. Crashkurs Java im Modul Algorithmen und Datenstrukturen
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</a>
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</li>
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<li class="md-nav__item">
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<a href="#01_hello_world" class="md-nav__link">
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2. 01: Hello World
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<a href="#02_basics" class="md-nav__link">
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3. 02: Basics
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<a href="#03_coding_style" class="md-nav__link">
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4. 03: Coding Style
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<li class="md-nav__item">
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<a href="#04_introduction_to_objects" class="md-nav__link">
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5. 04: Einführung in Objekte
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</a>
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<li class="md-nav__item">
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<a href="#05_types_of_objects" class="md-nav__link">
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6. 05: Typen von Objekten
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</a>
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<li class="md-nav__item">
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<a href="#06_java_docs" class="md-nav__link">
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7. 06: JavaDoc
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1. Crashkurs Java im Modul Algorithmen und Datenstrukturen
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</a>
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|
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<li class="md-nav__item">
|
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<a href="#01_hello_world" class="md-nav__link">
|
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2. 01: Hello World
|
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</a>
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</li>
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|
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<li class="md-nav__item">
|
|
<a href="#02_basics" class="md-nav__link">
|
|
3. 02: Basics
|
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</a>
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|
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</li>
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|
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<li class="md-nav__item">
|
|
<a href="#03_coding_style" class="md-nav__link">
|
|
4. 03: Coding Style
|
|
</a>
|
|
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</li>
|
|
|
|
<li class="md-nav__item">
|
|
<a href="#04_introduction_to_objects" class="md-nav__link">
|
|
5. 04: Einführung in Objekte
|
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</a>
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|
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</li>
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|
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<li class="md-nav__item">
|
|
<a href="#05_types_of_objects" class="md-nav__link">
|
|
6. 05: Typen von Objekten
|
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</a>
|
|
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</li>
|
|
|
|
<li class="md-nav__item">
|
|
<a href="#06_java_docs" class="md-nav__link">
|
|
7. 06: JavaDoc
|
|
</a>
|
|
|
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</li>
|
|
|
|
</ul>
|
|
|
|
</nav>
|
|
</div>
|
|
</div>
|
|
</div>
|
|
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|
|
|
<div class="md-content" data-md-component="content">
|
|
<article class="md-content__inner md-typeset">
|
|
|
|
|
|
|
|
|
|
|
|
<div id="print-site-page" class="print-site-enumerate-headings print-site-enumerate-figures">
|
|
<div id="print-site-banner">
|
|
<p>
|
|
<em>This box will disappear when printing</em>
|
|
<span style="float: right"><a href="https://timvink.github.io/mkdocs-print-site-plugin/">mkdocs-print-site-plugin</a></span>
|
|
</p>
|
|
<p>
|
|
This page has combined all site pages into one. You can export to PDF using <b>File > Print > Save as PDF</b>.
|
|
</p>
|
|
<p>
|
|
See also <a href="https://timvink.github.io/mkdocs-print-site-plugin/how-to/export-PDF.html">export to PDF</a> and <a href="https://timvink.github.io/mkdocs-print-site-plugin/how-to/export-HTML.html">export to standalone HTML</a>.
|
|
</p>
|
|
</div>
|
|
|
|
<section class="print-page">
|
|
<div id="print-page-toc" data-toc-depth="3">
|
|
<nav role='navigation' class='print-page-toc-nav'>
|
|
<h1 class='print-page-toc-title'>Index</h1>
|
|
</nav>
|
|
</div>
|
|
</section>
|
|
<section class="print-page" id="index"><h1 id="index-crashkurs-java-im-modul-algorithmen-und-datenstrukturen">Crashkurs Java im Modul Algorithmen und Datenstrukturen</h1>
|
|
<div class="highlight"><pre><span></span><code><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Main</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"Die Seite ist noch leer"</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
<span class="p">}</span><span class="w"></span>
|
|
</code></pre></div></section><section class="print-page" id="01_hello_world"><h1 id="01_hello_world-01-hello-world">01: Hello World</h1>
|
|
<h2 id="01_hello_world-approach-1-simple-string-output">Approach 1: Simple String Output</h2>
|
|
<p><div class="highlight"><pre><span></span><code><span class="c1">// main.java</span><span class="w"></span>
|
|
<span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">main</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"Hello, World!"</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
<span class="p">}</span><span class="w"></span>
|
|
</code></pre></div>
|
|
<div class="highlight"><pre><span></span><code>>> javac main.java
|
|
>> java main
|
|
Hello, World!
|
|
</code></pre></div></p>
|
|
<p>Was sagt dieser Code nun aus?
|
|
* Eine Klasse "main" ist öffentlich
|
|
* Dem Compiler wird die statische Methode <code>main</code> vorlegt
|
|
* Diese wird bei jedem Java Code genutzt
|
|
* Wir rufen die Klasse System auf und führen einen <code>println</code>-Befehl aus
|
|
* <code>Hello, World!</code> wird in der Konsole ausgegeben</p>
|
|
<h2 id="01_hello_world-approach-2-using-console-arguments">Approach 2: Using Console Arguments</h2>
|
|
<p><div class="highlight"><pre><span></span><code><span class="c1">// main.java</span><span class="w"></span>
|
|
<span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">main</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">args</span><span class="o">[</span><span class="mi">0</span><span class="o">]</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">" "</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">args</span><span class="o">[</span><span class="mi">1</span><span class="o">]</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
<span class="p">}</span><span class="w"></span>
|
|
</code></pre></div>
|
|
<div class="highlight"><pre><span></span><code>>> javac main.java
|
|
>> java main Hello, World!
|
|
Hello, World!
|
|
</code></pre></div></p>
|
|
<p>Was ist nun anders?
|
|
* Die Main-Methode übergibt standardmäßig Konsolenargumente als Array vom Typ String mit dem Namen <code>args</code>
|
|
* Jedes Argument hat einen Index im Array
|
|
* Für 2 Argumente rufen wir die ersten zwei Indexes auf, beginnend bei <code>0</code></p></section><section class="print-page" id="02_basics"><h1 id="02_basics-02-basics">02: Basics</h1>
|
|
<h2 id="02_basics-table-of-contents">Table of Contents</h2>
|
|
<ol>
|
|
<li><a href="#02_basics-nutzung-der-konsole">Nutzung der Konsole</a></li>
|
|
<li><a href="#02_basics-primitive-datentypen">Primitive Datentypen</a></li>
|
|
<li><a href="#02_basics-">Nicht Primitive Datentypen</a></li>
|
|
<li><a href="#02_basics-">Operatoren</a></li>
|
|
<li><a href="#02_basics-">Bedingungen</a></li>
|
|
<li><a href="#02_basics-">Schleifen</a></li>
|
|
<li><a href="#02_basics-exceptions">Exceptions</a></li>
|
|
</ol>
|
|
<h2 id="02_basics-nutzung-der-konsole">Nutzung der Konsole</h2>
|
|
<h3 id="02_basics-ausgabe">Ausgabe</h3>
|
|
<div class="highlight"><pre><span></span><code><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"print me and create a new line"</span><span class="p">);</span><span class="w"></span>
|
|
<span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">();</span><span class="w"> </span><span class="c1">// prints nothing but creates new line afterwards</span><span class="w"></span>
|
|
|
|
<span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">print</span><span class="p">(</span><span class="s">"print me without a new line | "</span><span class="p">);</span><span class="w"></span>
|
|
<span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">print</span><span class="p">(</span><span class="s">"print me but add a new line \n"</span><span class="p">);</span><span class="w"></span>
|
|
<span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">print</span><span class="p">(</span><span class="s">"yeah, this is on the new line! \n"</span><span class="p">);</span><span class="w"></span>
|
|
<span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">();</span><span class="w"> </span><span class="c1">// prints nothing but creates new line afterwards</span><span class="w"></span>
|
|
|
|
<span class="c1">// https://www.digitalocean.com/community/tutorials/java-printf-method</span><span class="w"></span>
|
|
<span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">"%s %s \n"</span><span class="p">,</span><span class="w"> </span><span class="s">"parameter 1"</span><span class="p">,</span><span class="w"> </span><span class="s">"parameter 2"</span><span class="p">);</span><span class="w"></span>
|
|
<span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">printf</span><span class="p">(</span><span class="s">"%s %e %f"</span><span class="p">,</span><span class="w"> </span><span class="s">"10.50"</span><span class="p">,</span><span class="w"> </span><span class="mf">10.50</span><span class="p">,</span><span class="w"> </span><span class="mf">10.50</span><span class="p">);</span><span class="w"></span>
|
|
</code></pre></div>
|
|
<h3 id="02_basics-eingabe">Eingabe</h3>
|
|
<div class="highlight"><pre><span></span><code><span class="kn">import</span><span class="w"> </span><span class="nn">java.util.Scanner</span><span class="p">;</span><span class="w"></span>
|
|
|
|
<span class="c1">// class and method : start</span><span class="w"></span>
|
|
<span class="n">Scanner</span><span class="w"> </span><span class="n">myScanner</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Scanner</span><span class="p">(</span><span class="n">System</span><span class="p">.</span><span class="na">in</span><span class="p">);</span><span class="w"></span>
|
|
<span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">print</span><span class="p">(</span><span class="s">"Enter Username: "</span><span class="p">);</span><span class="w"></span>
|
|
<span class="n">String</span><span class="w"> </span><span class="n">username</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">myScanner</span><span class="p">.</span><span class="na">nextLine</span><span class="p">();</span><span class="w"></span>
|
|
<span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">print</span><span class="p">(</span><span class="s">"Enter Password: "</span><span class="p">);</span><span class="w"></span>
|
|
<span class="n">String</span><span class="w"> </span><span class="n">password</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">myScanner</span><span class="p">.</span><span class="na">nextLine</span><span class="p">();</span><span class="w"></span>
|
|
<span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"your Username: "</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">username</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">"\nyour password: "</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">password</span><span class="w"> </span><span class="p">);</span><span class="w"></span>
|
|
<span class="c1">// class and method : end</span><span class="w"></span>
|
|
</code></pre></div>
|
|
<h2 id="02_basics-primitive-datentypen">Primitive Datentypen</h2>
|
|
<p>Quelle: <a href="https://www.w3schools.com/java/java_data_types.asp">w3schools.com</a></p>
|
|
<table>
|
|
<thead>
|
|
<tr>
|
|
<th>Data Type</th>
|
|
<th>Size</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
</thead>
|
|
<tbody>
|
|
<tr>
|
|
<td>byte</td>
|
|
<td>1 byte</td>
|
|
<td>Stores whole numbers from -128 to 127</td>
|
|
</tr>
|
|
<tr>
|
|
<td>short</td>
|
|
<td>2 bytes</td>
|
|
<td>Stores whole numbers from -32,768 to 32,767</td>
|
|
</tr>
|
|
<tr>
|
|
<td>int</td>
|
|
<td>4 bytes</td>
|
|
<td>Stores whole numbers from -2,147,483,648 to 2,147,483,647</td>
|
|
</tr>
|
|
<tr>
|
|
<td>long</td>
|
|
<td>8 bytes</td>
|
|
<td>Stores whole numbers from -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807</td>
|
|
</tr>
|
|
<tr>
|
|
<td>float</td>
|
|
<td>4 bytes</td>
|
|
<td>Stores fractional numbers. Sufficient for storing 6 to 7 decimal digits</td>
|
|
</tr>
|
|
<tr>
|
|
<td>double</td>
|
|
<td>8 bytes</td>
|
|
<td>Stores fractional numbers. Sufficient for storing 15 decimal digits</td>
|
|
</tr>
|
|
<tr>
|
|
<td>boolean</td>
|
|
<td>1 bit</td>
|
|
<td>Stores true or false values</td>
|
|
</tr>
|
|
<tr>
|
|
<td>char</td>
|
|
<td>2 bytes</td>
|
|
<td>Stores a single character/letter or ASCII values</td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<h3 id="02_basics-type-casting">Type Casting</h3>
|
|
<p>Bei Type Casting handelt es sich um das überführen eines primitiven Datentypen
|
|
in einen anderen.</p>
|
|
<p>Quelle: <a href="https://www.w3schools.com/java/java_type_casting.asp">w3schools.com</a></p>
|
|
<h4 id="02_basics-widening-casting-automatically">Widening Casting (automatically)</h4>
|
|
<p>Hier wird ein kleinerer Typ in einen größeren Typ konvertiert</p>
|
|
<p><code>byte</code> -> <code>short</code> -> <code>char</code> -> <code>int</code> -> <code>long</code> -> <code>float</code> -> <code>double</code></p>
|
|
<div class="highlight"><pre><span></span><code><span class="kt">int</span><span class="w"> </span><span class="n">myInt</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">9</span><span class="p">;</span><span class="w"></span>
|
|
<span class="kt">double</span><span class="w"> </span><span class="n">myDouble</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">myInt</span><span class="p">;</span><span class="w"> </span><span class="c1">// Automatic casting: int to double</span><span class="w"></span>
|
|
|
|
<span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">myInt</span><span class="p">);</span><span class="w"> </span><span class="c1">// Outputs 9</span><span class="w"></span>
|
|
<span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">myDouble</span><span class="p">);</span><span class="w"> </span><span class="c1">// Outputs 9.0</span><span class="w"></span>
|
|
</code></pre></div>
|
|
<h4 id="02_basics-narrowing-casting-manually">Narrowing Casting (manually)</h4>
|
|
<p>Hier wird ein größerer Typ in einen kleineren Typ konvertiert</p>
|
|
<p><code>double</code> -> <code>float</code> -> <code>long</code> -> <code>int</code> -> <code>char</code> -> <code>short</code> -> <code>byte</code></p>
|
|
<div class="highlight"><pre><span></span><code><span class="kt">double</span><span class="w"> </span><span class="n">myDouble</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mf">9.78d</span><span class="p">;</span><span class="w"></span>
|
|
<span class="kt">int</span><span class="w"> </span><span class="n">myInt</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="p">)</span><span class="w"> </span><span class="n">myDouble</span><span class="p">;</span><span class="w"> </span><span class="c1">// Manual casting: double to int</span><span class="w"></span>
|
|
|
|
<span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">myDouble</span><span class="p">);</span><span class="w"> </span><span class="c1">// Outputs 9.78</span><span class="w"></span>
|
|
<span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">myInt</span><span class="p">);</span><span class="w"> </span><span class="c1">// Outputs 9</span><span class="w"></span>
|
|
</code></pre></div>
|
|
<h2 id="02_basics-nicht-primitive-datentypen">Nicht Primitive Datentypen</h2>
|
|
<h3 id="02_basics-string">String</h3>
|
|
<p>String ist eine Wrapperklasse, welche eine Zeichenkette aus einzelnen chars
|
|
zusammenbaut. In manchen Programmiersprachen (z.B. C++) ist ein String
|
|
vergleichbar mit einem char-Array.</p>
|
|
<div class="highlight"><pre><span></span><code><span class="n">String</span><span class="w"> </span><span class="n">myString</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">"this is a text"</span><span class="p">;</span><span class="w"></span>
|
|
<span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"myString: "</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">myString</span><span class="p">);</span><span class="w"></span>
|
|
|
|
<span class="n">String</span><span class="w"> </span><span class="n">concatString</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">"hello"</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">"World"</span><span class="p">;</span><span class="w"></span>
|
|
<span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"concatString: "</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">concatString</span><span class="p">);</span><span class="w"></span>
|
|
</code></pre></div>
|
|
<p>Methoden der Standardbibliothek:
|
|
<div class="highlight"><pre><span></span><code><span class="n">myString</span><span class="p">.</span><span class="na">charAt</span><span class="p">();</span><span class="w"> </span><span class="c1">// Returns the char value at the specified index.</span><span class="w"></span>
|
|
<span class="n">myString</span><span class="p">.</span><span class="na">indexOf</span><span class="p">();</span><span class="w"> </span><span class="c1">// Returns the index within this string of the first occurrence of the specified substring.</span><span class="w"></span>
|
|
<span class="n">myString</span><span class="p">.</span><span class="na">substring</span><span class="p">();</span><span class="w"> </span><span class="c1">// Returns a string that is a substring of this string.</span><span class="w"></span>
|
|
<span class="n">myString</span><span class="p">.</span><span class="na">equals</span><span class="p">();</span><span class="w"> </span><span class="c1">// Compares this string to the specified object.</span><span class="w"></span>
|
|
<span class="n">myString</span><span class="p">.</span><span class="na">toLowerCase</span><span class="p">();</span><span class="w"> </span><span class="c1">// Converts all of the characters in this String to lower case.</span><span class="w"></span>
|
|
<span class="n">myString</span><span class="p">.</span><span class="na">toUpperCase</span><span class="p">();</span><span class="w"> </span><span class="c1">// Converts all of the characters in this String to upper case.</span><span class="w"></span>
|
|
<span class="n">myString</span><span class="p">.</span><span class="na">contains</span><span class="p">();</span><span class="w"> </span><span class="c1">// Returns true if and only if this string contains the specified sequence of char values.</span><span class="w"></span>
|
|
<span class="n">myString</span><span class="p">.</span><span class="na">replaceAll</span><span class="p">();</span><span class="w"> </span><span class="c1">// Replaces each substring of this string that matches the given regular expression with the given replacement.</span><span class="w"></span>
|
|
<span class="n">myString</span><span class="p">.</span><span class="na">compareTo</span><span class="p">();</span><span class="w"> </span><span class="c1">// Compares two strings lexicographically. The comparison is based on the Unicode value of each character in the strings.</span><span class="w"></span>
|
|
</code></pre></div></p>
|
|
<h3 id="02_basics-numeric-datatypes">Numeric Datatypes</h3>
|
|
<p>Im Gegensatz zu den primitiven Datentypen werden hier "Wrapper" verwendet, um
|
|
dynamisch mit den Werten arbeiten zu können. Das erlaubt auch die Erweiterung
|
|
um verschiedene Methoden in der Standardbibliothek.</p>
|
|
<p>Integer:
|
|
<div class="highlight"><pre><span></span><code><span class="n">Integer</span><span class="w"> </span><span class="n">myNumber</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">10</span><span class="p">;</span><span class="w"></span>
|
|
<span class="n">Integer</span><span class="p">.</span><span class="na">parseInt</span><span class="p">();</span><span class="w"> </span><span class="c1">// Parses the string argument as a signed decimal integer.</span><span class="w"></span>
|
|
<span class="n">Integer</span><span class="p">.</span><span class="na">parseUnsignedInt</span><span class="p">();</span><span class="w"> </span><span class="c1">// Parses the string argument as an unsigned decimal integer.</span><span class="w"></span>
|
|
<span class="n">Integer</span><span class="p">.</span><span class="na">valueOf</span><span class="p">();</span><span class="w"> </span><span class="c1">// Returns an Integer object holding the value of the specified String.</span><span class="w"></span>
|
|
</code></pre></div></p>
|
|
<p>Float and Double:
|
|
<div class="highlight"><pre><span></span><code><span class="n">Double</span><span class="w"> </span><span class="n">myDouble</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mf">10.0</span><span class="p">;</span><span class="w"></span>
|
|
<span class="n">myDouble</span><span class="p">.</span><span class="na">isNaN</span><span class="p">();</span><span class="w"> </span><span class="c1">// Returns true if this Double value is a Not-a-Number (NaN), false otherwise.</span><span class="w"></span>
|
|
|
|
<span class="n">Float</span><span class="w"> </span><span class="n">myFloat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">float</span><span class="p">)</span><span class="mf">10.0</span><span class="p">;</span><span class="w"></span>
|
|
<span class="n">myFloat</span><span class="p">.</span><span class="na">isNaN</span><span class="p">();</span><span class="w"> </span><span class="c1">// Returns true if this Float value is a Not-a-Number (NaN), false otherwise</span><span class="w"></span>
|
|
</code></pre></div></p>
|
|
<p>Funktionen für alle Numerischen Datentypen (Nicht Primitiv):
|
|
<div class="highlight"><pre><span></span><code><span class="n">myNumber</span><span class="p">.</span><span class="na">compareTo</span><span class="p">();</span><span class="w"> </span><span class="c1">// Compares two Integer objects numerically.</span><span class="w"></span>
|
|
<span class="n">myNumber</span><span class="p">.</span><span class="na">toString</span><span class="p">();</span><span class="w"> </span><span class="c1">// Returns a String object representing this Integer's value.</span><span class="w"></span>
|
|
<span class="n">myNumber</span><span class="p">.</span><span class="na">intValue</span><span class="p">();</span><span class="w"> </span><span class="c1">// Returns the value of this Integer as an int.</span><span class="w"></span>
|
|
<span class="n">myNumber</span><span class="p">.</span><span class="na">floatValue</span><span class="p">();</span><span class="w"> </span><span class="c1">// Returns the value of this Integer as a float after a widening primitive conversion.</span><span class="w"></span>
|
|
<span class="n">myNumber</span><span class="p">.</span><span class="na">doubleValue</span><span class="p">();</span><span class="w"> </span><span class="c1">// Returns the value of this Integer as a double after a widening primitive conversion.</span><span class="w"></span>
|
|
<span class="n">myNumber</span><span class="p">.</span><span class="na">shortValue</span><span class="p">();</span><span class="w"> </span><span class="c1">// Returns the value of this Integer as a short after a narrowing primitive conversion.</span><span class="w"></span>
|
|
</code></pre></div></p>
|
|
<h3 id="02_basics-arrays">Arrays</h3>
|
|
<p>Bei Arrays handelt es sich um Schleifen eines bestimmten Datentypen. Sie werden
|
|
verwendet, um mehrere Werte in einer Variable zu speichern.</p>
|
|
<div class="highlight"><pre><span></span><code><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">myStringArray</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">String</span><span class="o">[</span><span class="mi">3</span><span class="o">]</span><span class="p">;</span><span class="w"></span>
|
|
<span class="n">myStringArray</span><span class="o">[</span><span class="mi">0</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">"ROT"</span><span class="p">;</span><span class="w"></span>
|
|
<span class="n">myStringArray</span><span class="o">[</span><span class="mi">1</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">"GRÜN"</span><span class="p">;</span><span class="w"></span>
|
|
<span class="n">myStringArray</span><span class="o">[</span><span class="mi">2</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">"BLAU"</span><span class="p">;</span><span class="w"></span>
|
|
|
|
<span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">myIntArray</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="mi">0</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">};</span><span class="w"></span>
|
|
|
|
<span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">myIntArray</span><span class="p">.</span><span class="na">length</span><span class="p">);</span><span class="w"> </span><span class="c1">// 3</span><span class="w"></span>
|
|
<span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Arrays</span><span class="p">.</span><span class="na">toString</span><span class="p">(</span><span class="n">myIntArray</span><span class="p">));</span><span class="w"> </span><span class="c1">// [0,1,2]</span><span class="w"></span>
|
|
</code></pre></div>
|
|
<p>multidimensionale Arrays:
|
|
<div class="highlight"><pre><span></span><code><span class="kt">int</span><span class="o">[][]</span><span class="w"> </span><span class="n">my2DArray</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">{</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">},</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">{</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="mi">5</span><span class="p">},</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">{</span><span class="mi">6</span><span class="p">,</span><span class="w"> </span><span class="mi">7</span><span class="p">,</span><span class="w"> </span><span class="mi">8</span><span class="p">,</span><span class="w"> </span><span class="mi">9</span><span class="p">},</span><span class="w"></span>
|
|
<span class="p">};</span><span class="w"></span>
|
|
|
|
<span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">my2DArray</span><span class="p">.</span><span class="na">length</span><span class="p">);</span><span class="w"></span>
|
|
<span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">my2DArray</span><span class="o">[</span><span class="mi">0</span><span class="o">]</span><span class="p">.</span><span class="na">length</span><span class="p">);</span><span class="w"></span>
|
|
|
|
<span class="k">for</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">row</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span><span class="w"> </span><span class="n">row</span><span class="w"> </span><span class="o"><</span><span class="w"> </span><span class="n">my2DArray</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">row</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">print</span><span class="p">(</span><span class="s">"["</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">for</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">column</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span><span class="w"> </span><span class="n">column</span><span class="w"> </span><span class="o"><</span><span class="w"> </span><span class="n">my2DArray</span><span class="o">[</span><span class="n">row</span><span class="o">]</span><span class="p">.</span><span class="na">length</span><span class="p">;</span><span class="w"> </span><span class="n">column</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">column</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="p">(</span><span class="n">my2DArray</span><span class="o">[</span><span class="n">row</span><span class="o">]</span><span class="p">.</span><span class="na">length</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">1</span><span class="p">)</span><span class="w"> </span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">print</span><span class="p">(</span><span class="n">my2DArray</span><span class="o">[</span><span class="n">row</span><span class="o">][</span><span class="n">column</span><span class="o">]</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">continue</span><span class="p">;</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">print</span><span class="p">(</span><span class="n">my2DArray</span><span class="o">[</span><span class="n">row</span><span class="o">][</span><span class="n">column</span><span class="o">]</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">", "</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"]"</span><span class="p">);</span><span class="w"></span>
|
|
<span class="p">}</span><span class="w"></span>
|
|
</code></pre></div></p>
|
|
<p>Methoden:
|
|
<div class="highlight"><pre><span></span><code><span class="n">Arrays</span><span class="p">.</span><span class="na">toString</span><span class="p">(</span><span class="n">myArray</span><span class="p">);</span><span class="w"> </span><span class="c1">// a string representation of the object.</span><span class="w"></span>
|
|
<span class="n">Arrays</span><span class="p">.</span><span class="na">copyOf</span><span class="p">(</span><span class="n">myArray</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p">);</span><span class="w"> </span><span class="c1">// Copies the specified array, truncating or padding with zeros (if necessary) so the copy has the specified length.</span><span class="w"></span>
|
|
<span class="n">Arrays</span><span class="p">.</span><span class="na">compare</span><span class="p">(</span><span class="n">myArray</span><span class="p">,</span><span class="w"> </span><span class="n">myArray</span><span class="p">);</span><span class="w"> </span><span class="c1">// Compares two int arrays lexicographically.</span><span class="w"></span>
|
|
<span class="n">Arrays</span><span class="p">.</span><span class="na">equals</span><span class="p">(</span><span class="n">myArray</span><span class="p">,</span><span class="w"> </span><span class="n">myArray</span><span class="p">);</span><span class="w"> </span><span class="c1">// Returns true if the two specified arrays of ints are equal to one another.</span><span class="w"></span>
|
|
<span class="n">Arrays</span><span class="p">.</span><span class="na">sort</span><span class="p">(</span><span class="n">myArray</span><span class="p">);</span><span class="w"> </span><span class="c1">// Sorts the specified array into ascending numerical order</span><span class="w"></span>
|
|
<span class="n">Arrays</span><span class="p">.</span><span class="na">fill</span><span class="p">(</span><span class="n">myArray</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p">);</span><span class="w"> </span><span class="c1">// Assigns the specified int value to each element of the specified array of ints.</span><span class="w"></span>
|
|
</code></pre></div></p>
|
|
<h2 id="02_basics-operatoren">Operatoren</h2>
|
|
<h3 id="02_basics-arithmetic-operators">Arithmetic Operators</h3>
|
|
<div class="highlight"><pre><span></span><code><span class="kt">int</span><span class="w"> </span><span class="n">calcAddition</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">20</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">10</span><span class="p">;</span><span class="w"> </span><span class="c1">// = 30</span><span class="w"></span>
|
|
<span class="kt">int</span><span class="w"> </span><span class="n">calcSubstraction</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">20</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="mi">10</span><span class="p">;</span><span class="w"> </span><span class="c1">// = 10</span><span class="w"></span>
|
|
<span class="kt">int</span><span class="w"> </span><span class="n">calcMultiplication</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">20</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">10</span><span class="p">;</span><span class="w"> </span><span class="c1">// = 200</span><span class="w"></span>
|
|
<span class="kt">int</span><span class="w"> </span><span class="n">calcDivision</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">20</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">10</span><span class="p">;</span><span class="w"> </span><span class="c1">// = 2</span><span class="w"></span>
|
|
<span class="kt">int</span><span class="w"> </span><span class="n">calcModulus</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">20</span><span class="w"> </span><span class="o">%</span><span class="w"> </span><span class="mi">3</span><span class="p">;</span><span class="w"> </span><span class="c1">// = 2</span><span class="w"></span>
|
|
|
|
<span class="kt">int</span><span class="w"> </span><span class="n">myNumber</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">10</span><span class="p">;</span><span class="w"></span>
|
|
<span class="n">myNumber</span><span class="o">++</span><span class="p">;</span><span class="w"> </span><span class="c1">// myNumber = 11</span><span class="w"></span>
|
|
<span class="n">myNumber</span><span class="o">--</span><span class="p">;</span><span class="w"> </span><span class="c1">// myNumber = 10</span><span class="w"></span>
|
|
<span class="n">myNumber</span><span class="o">--</span><span class="p">;</span><span class="w"> </span><span class="c1">// myNumber = 9</span><span class="w"></span>
|
|
</code></pre></div>
|
|
<h3 id="02_basics-comparison-operators">Comparison Operators</h3>
|
|
<div class="highlight"><pre><span></span><code><span class="kt">int</span><span class="w"> </span><span class="n">biggerNumber</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">20</span><span class="p">;</span><span class="w"></span>
|
|
<span class="kt">int</span><span class="w"> </span><span class="n">biggerNumberAgain</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">20</span><span class="p">;</span><span class="w"></span>
|
|
<span class="kt">int</span><span class="w"> </span><span class="n">smallerNumber</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">10</span><span class="p">;</span><span class="w"></span>
|
|
|
|
<span class="c1">// (20 == 20) => true</span><span class="w"></span>
|
|
<span class="c1">// (20 != 20) => false</span><span class="w"></span>
|
|
<span class="c1">// (20 > 10) => true</span><span class="w"></span>
|
|
<span class="c1">// (20 < 10) => false</span><span class="w"></span>
|
|
<span class="c1">// (20 >= 10) => true</span><span class="w"></span>
|
|
<span class="c1">// (20 >= 10) => true</span><span class="w"></span>
|
|
</code></pre></div>
|
|
<h2 id="02_basics-bedingungen">Bedingungen</h2>
|
|
<p>wir verwenden folgende Variablen:
|
|
<div class="highlight"><pre><span></span><code><span class="kt">int</span><span class="w"> </span><span class="n">biggerNumber</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">20</span><span class="p">;</span><span class="w"></span>
|
|
<span class="kt">int</span><span class="w"> </span><span class="n">biggerNumberAgain</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">20</span><span class="p">;</span><span class="w"></span>
|
|
<span class="kt">int</span><span class="w"> </span><span class="n">smallerNumber</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">10</span><span class="p">;</span><span class="w"></span>
|
|
</code></pre></div></p>
|
|
<h3 id="02_basics-if-condition-better-version">if-condition (better version)</h3>
|
|
<div class="highlight"><pre><span></span><code><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">biggerNumber</span><span class="w"> </span><span class="o">></span><span class="w"> </span><span class="n">smallerNumber</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"the left number is bigger!"</span><span class="p">);</span><span class="w"></span>
|
|
<span class="p">}</span><span class="w"></span>
|
|
</code></pre></div>
|
|
<h3 id="02_basics-if-condition-worse-version">if-condition (worse version)</h3>
|
|
<div class="highlight"><pre><span></span><code><span class="c1">// prefer to not write it down like this!</span><span class="w"></span>
|
|
<span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">biggerNumber</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">biggerNumberAgain</span><span class="p">)</span><span class="w"> </span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"We don't do this here..."</span><span class="p">);</span><span class="w"></span>
|
|
</code></pre></div>
|
|
<h3 id="02_basics-if-else-condition">if-else-condition</h3>
|
|
<div class="highlight"><pre><span></span><code><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">biggerNumber</span><span class="w"> </span><span class="o"><</span><span class="w"> </span><span class="n">smallerNumber</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"the left number is smaller!"</span><span class="p">);</span><span class="w"></span>
|
|
<span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">biggerNumber</span><span class="w"> </span><span class="o"><</span><span class="w"> </span><span class="n">biggerNumberAgain</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"but this time, the left number is smaller!"</span><span class="p">);</span><span class="w"></span>
|
|
<span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"the left number is just too big!"</span><span class="p">);</span><span class="w"></span>
|
|
<span class="p">}</span><span class="w"></span>
|
|
</code></pre></div>
|
|
<h3 id="02_basics-switch-case">switch-case</h3>
|
|
<div class="highlight"><pre><span></span><code><span class="kt">int</span><span class="w"> </span><span class="n">luckyNumber</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">69</span><span class="p">;</span><span class="w"></span>
|
|
<span class="k">switch</span><span class="w"> </span><span class="p">(</span><span class="n">luckyNumber</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">case</span><span class="w"> </span><span class="mi">13</span><span class="p">:</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"some people consider 13 to be a lucky number"</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">break</span><span class="p">;</span><span class="w"> </span><span class="c1">// we need this to avoid default!</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">case</span><span class="w"> </span><span class="mi">7</span><span class="p">:</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"slot machines value this number high"</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">break</span><span class="p">;</span><span class="w"> </span><span class="c1">// we need this to avoid default!</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">default</span><span class="p">:</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"seems, your number was not lucky enough..."</span><span class="p">);</span><span class="w"></span>
|
|
<span class="p">}</span><span class="w"></span>
|
|
</code></pre></div>
|
|
<h2 id="02_basics-schleifen">Schleifen</h2>
|
|
<h3 id="02_basics-while-loop">while-loop</h3>
|
|
<div class="highlight"><pre><span></span><code><span class="kt">int</span><span class="w"> </span><span class="n">whileNumber</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">3</span><span class="p">;</span><span class="w"></span>
|
|
<span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">whileNumber</span><span class="w"> </span><span class="o">></span><span class="w"> </span><span class="mi">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">whileNumber</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">whileNumber</span><span class="w"> </span><span class="o">--</span><span class="p">;</span><span class="w"></span>
|
|
<span class="p">}</span><span class="w"></span>
|
|
</code></pre></div>
|
|
<h3 id="02_basics-do-while-loop">do-while-loop</h3>
|
|
<div class="highlight"><pre><span></span><code><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"--- doWhileNumber:"</span><span class="p">);</span><span class="w"></span>
|
|
<span class="kt">int</span><span class="w"> </span><span class="n">doWhileNumber</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">3</span><span class="p">;</span><span class="w"></span>
|
|
<span class="k">do</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">doWhileNumber</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">doWhileNumber</span><span class="o">--</span><span class="p">;</span><span class="w"></span>
|
|
<span class="p">}</span><span class="w"> </span><span class="k">while</span><span class="p">(</span><span class="n">doWhileNumber</span><span class="w"> </span><span class="o">></span><span class="w"> </span><span class="mi">0</span><span class="p">);</span><span class="w"></span>
|
|
</code></pre></div>
|
|
<h3 id="02_basics-for-loop">for-loop</h3>
|
|
<div class="highlight"><pre><span></span><code><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"--- forNumber:"</span><span class="p">);</span><span class="w"></span>
|
|
<span class="k">for</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">iterator</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span><span class="w"> </span><span class="n">iterator</span><span class="w"> </span><span class="o"><=</span><span class="w"> </span><span class="mi">5</span><span class="p">;</span><span class="w"> </span><span class="n">iterator</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">iterator</span><span class="p">);</span><span class="w"></span>
|
|
<span class="p">}</span><span class="w"></span>
|
|
</code></pre></div>
|
|
<h3 id="02_basics-beispiel-ausfuhrung">Beispiel Ausführung</h3>
|
|
<div class="highlight"><pre><span></span><code><span class="kt">int</span><span class="w"> </span><span class="n">myNumber</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span><span class="w"></span>
|
|
<span class="c1">// count, how many times we can add 2 until we reach 16,</span><span class="w"></span>
|
|
<span class="c1">// but we pretend, 13 doesn't exist for reasons</span><span class="w"></span>
|
|
<span class="k">for</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">counter</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span><span class="w"> </span><span class="n">counter</span><span class="w"> </span><span class="o"><=</span><span class="w"> </span><span class="mi">10</span><span class="p">;</span><span class="w"> </span><span class="n">counter</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">myNumber</span><span class="w"> </span><span class="o">+=</span><span class="w"> </span><span class="mi">2</span><span class="p">;</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">myNumber</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">13</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">continue</span><span class="p">;</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">counter</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">myNumber</span><span class="w"> </span><span class="o">>=</span><span class="w"> </span><span class="mi">16</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">break</span><span class="p">;</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
<span class="p">}</span><span class="w"></span>
|
|
</code></pre></div>
|
|
<h3 id="02_basics-hinweis">Hinweis</h3>
|
|
<p>Vermeidet einfache Variablennamen wie i, u, usw.m um die Lesbarkeit einfach zu halten
|
|
<div class="highlight"><pre><span></span><code><span class="c1">// </span><span class="w"></span>
|
|
<span class="k">for</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o"><</span><span class="w"> </span><span class="mi">10</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">for</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">u</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">30</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">></span><span class="w"> </span><span class="mi">15</span><span class="p">;</span><span class="w"> </span><span class="n">u</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">myArray</span><span class="o">[</span><span class="n">u</span><span class="o">][</span><span class="n">i</span><span class="o">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">u</span><span class="p">;</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
<span class="p">}</span><span class="w"></span>
|
|
</code></pre></div></p>
|
|
<h3 id="02_basics-for-each-loop">for-each-loop</h3>
|
|
<h4 id="02_basics-arrays_1">arrays</h4>
|
|
<div class="highlight"><pre><span></span><code><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">myArray</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p">};</span><span class="w"></span>
|
|
|
|
<span class="k">for</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">selectedValue</span><span class="p">:</span><span class="w"> </span><span class="n">myArray</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"myArray: "</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">selectedValue</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">selectedValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span><span class="w"></span>
|
|
<span class="p">}</span><span class="w"></span>
|
|
|
|
<span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">Arrays</span><span class="p">.</span><span class="na">toString</span><span class="p">(</span><span class="n">myArray</span><span class="p">));</span><span class="w"></span>
|
|
|
|
<span class="k">for</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">selection</span><span class="p">:</span><span class="w"> </span><span class="n">myArray</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">selection</span><span class="p">);</span><span class="w"></span>
|
|
<span class="p">}</span><span class="w"></span>
|
|
</code></pre></div>
|
|
<h4 id="02_basics-lists">lists</h4>
|
|
<div class="highlight"><pre><span></span><code><span class="n">LinkedList</span><span class="o"><</span><span class="n">String</span><span class="o">></span><span class="w"> </span><span class="n">myLinkedList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">LinkedList</span><span class="o"><></span><span class="p">();</span><span class="w"></span>
|
|
<span class="n">myLinkedList</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">"List_1"</span><span class="p">);</span><span class="w"></span>
|
|
<span class="n">myLinkedList</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">"List_2"</span><span class="p">);</span><span class="w"></span>
|
|
<span class="n">myLinkedList</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="s">"List_3"</span><span class="p">);</span><span class="w"></span>
|
|
|
|
<span class="k">for</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">selectedValue</span><span class="p">:</span><span class="w"> </span><span class="n">myArray</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">selectedValue</span><span class="p">);</span><span class="w"></span>
|
|
<span class="p">}</span><span class="w"></span>
|
|
</code></pre></div>
|
|
<h3 id="02_basics-maps">maps</h3>
|
|
<div class="highlight"><pre><span></span><code><span class="n">HashMap</span><span class="o"><</span><span class="n">Integer</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="o">></span><span class="w"> </span><span class="n">myHashMap</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HashMap</span><span class="o"><></span><span class="p">();</span><span class="w"></span>
|
|
<span class="n">myHashMap</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="s">"Larry"</span><span class="p">);</span><span class="w"></span>
|
|
<span class="n">myHashMap</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="s">"Steve"</span><span class="p">);</span><span class="w"></span>
|
|
<span class="n">myHashMap</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="s">"James"</span><span class="p">);</span><span class="w"></span>
|
|
|
|
<span class="n">myHashMap</span><span class="p">.</span><span class="na">forEach</span><span class="p">((</span><span class="n">key</span><span class="p">,</span><span class="w"> </span><span class="n">value</span><span class="p">)</span><span class="w"> </span><span class="o">-></span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">key</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">" "</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">value</span><span class="p">);</span><span class="w"></span>
|
|
<span class="p">});</span><span class="w"></span>
|
|
</code></pre></div>
|
|
<h2 id="02_basics-exceptions">Exceptions</h2>
|
|
<div class="highlight"><pre><span></span><code><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Main</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
|
|
<span class="w"> </span><span class="c1">// simple exception handling</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">myNumbers</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p">};</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">myNumbers</span><span class="o">[</span><span class="mi">10</span><span class="o">]</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">Exception</span><span class="w"> </span><span class="n">exception</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">exception</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"---"</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
|
|
<span class="w"> </span><span class="c1">// extended exception handling</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">myNumbers</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p">};</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">printTenthIndex</span><span class="p">(</span><span class="n">myNumbers</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">RuntimeException</span><span class="w"> </span><span class="n">exception</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"class: "</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">exception</span><span class="p">.</span><span class="na">getClass</span><span class="p">());</span><span class="w"> </span><span class="c1">// class: class java.lang.RuntimeException</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"cause: "</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">exception</span><span class="p">.</span><span class="na">getCause</span><span class="p">());</span><span class="w"> </span><span class="c1">// cause: java.lang.RuntimeException: array is not big enough</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"message: "</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">exception</span><span class="p">.</span><span class="na">getMessage</span><span class="p">());</span><span class="w"> </span><span class="c1">// message: index was not found</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"finally! The 'try catch' is finished."</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
|
|
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">printTenthIndex</span><span class="p">(</span><span class="kt">int</span><span class="o">[]</span><span class="w"> </span><span class="n">array</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">RuntimeException</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">Exception</span><span class="w"> </span><span class="n">r</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">RuntimeException</span><span class="p">(</span><span class="s">"array is not big enough"</span><span class="p">);</span><span class="w"> </span><span class="c1">// not every exception supports causes</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">array</span><span class="p">.</span><span class="na">length</span><span class="w"> </span><span class="o"><</span><span class="w"> </span><span class="mi">11</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">RuntimeException</span><span class="p">(</span><span class="s">"index was not found"</span><span class="p">,</span><span class="w"> </span><span class="n">r</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">array</span><span class="o">[</span><span class="mi">10</span><span class="o">]</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
<span class="p">}</span><span class="w"></span>
|
|
</code></pre></div></section><section class="print-page" id="03_coding_style"><h1 id="03_coding_style-03-coding-style">03: Coding Style</h1>
|
|
<p>Programme können sehr schnell sehr komplex werden.
|
|
Daher ist es wichtig, sich an Stil-Regeln zu halten, um sie möglichst
|
|
verständlich zu schreiben.</p>
|
|
<h2 id="03_coding_style-1-selbsterklarend">1. Selbsterklärend</h2>
|
|
<p>Code sollte sich so gut wie möglich selbst erklären.
|
|
Dazu sind sprechende Variablen-, Funktions-, Klassennamen etc. erforderlich.
|
|
Kurze Namen sind nur in kleinen Gültigkeitsbereichen oder bei klarer Bedeutung
|
|
(z.B. <code>i</code> für for-Schleifen Iteratoren, <code>y</code> für vertikale Position) erlaubt.</p>
|
|
<h3 id="03_coding_style-11-kommentare">1.1 Kommentare</h3>
|
|
<p>Kommentare sind in diesem Zusammenhang vorallem zur Strukturierung/Abgrenzung
|
|
des Codes empfohlen, und um die
|
|
Verständlichkeit zu erhöhen.
|
|
Kommentare sollten nicht das Offensichtliche wiederholen (siehe Bild).</p>
|
|
<p><img alt="Cat labeled Cat" src="https://i.redd.it/iuy9fxt300811.png" /></p>
|
|
<p>Selbstverständlich kann Code zum besseren eigenen Verständnis kommentiert
|
|
werden.
|
|
Denken Sie aber daran, dass bei Code Änderungen auch die Kommentare mit gepflegt
|
|
werden müssen.</p>
|
|
<h2 id="03_coding_style-4-benennung">4. Benennung</h2>
|
|
<p>Die folgenden Regelungen sind empfohlen und in keinster Weise verpflichtend.</p>
|
|
<h3 id="03_coding_style-41-camelcase-fur-variablen-und-funktionen">4.1 camelCase für Variablen und Funktionen</h3>
|
|
<p>Variablen- und Funktionsnamen beginnen mit Kleinbuchstaben und folgen der
|
|
camelCase Notation, d.h. bei zusammengesetzten
|
|
Namen beginnen die Wortteile im Inneren mit einem Großbuchstaben.<br />
|
|
Funktionsnamen beschreiben dabei eine Aktivität (
|
|
z.B. <code>calculateHorizontalPosition()</code>) oder eine Frage (z.B. <code>isHit()</code>).</p>
|
|
<p>Gleiches gilt für Attribute und Methoden.</p>
|
|
<h3 id="03_coding_style-42-unterstrich-vor-formalen-parametern">4.2 Unterstrich vor formalen Parametern</h3>
|
|
<p>Formale Parameter folgen dem Variablen-Benennungs-Schema, mit dem Zusatz eines
|
|
Unterstriches am Anfang.
|
|
(z.B. <code>moveTo(_x: number, _y: number)</code>).</p>
|
|
<h3 id="03_coding_style-43-pascalcase-fur-klassen-und-interfaces">4.3 PascalCase für Klassen und Interfaces</h3>
|
|
<p>Die Namen von Klassen und Interfaces beginnen mit einem Großbuchstaben und
|
|
folgen sonst der Kamelnotation (also
|
|
PascalCase).<br />
|
|
Klassen und Interfaces beschreiben im Normalfall ein bestimmtes Objekt, nicht
|
|
eine Gruppe von Objekten.
|
|
Dies sollte sich im Namen wiederspiegeln (<code>Produkt</code> statt <code>Produkte</code>).</p>
|
|
<h3 id="03_coding_style-44-groschreibung-fur-enumeratoren">4.4 Großschreibung für Enumeratoren</h3>
|
|
<p>Die Namen von Enumerationen und deren Elemente werden durchgehend mit
|
|
Großbuchstaben geschreiben. Wortteile werden bei
|
|
Bedarf mit Unterstrich getrennt.</p>
|
|
<h2 id="03_coding_style-5-doppelte-und-einfache-anfuhrungszeichen">5. Doppelte und einfache Anführungszeichen</h2>
|
|
<p>Es empfielt sich, einfache Anführungszeichen <code>' '</code> für char und doppelte
|
|
Anführungszeichen <code>" "</code> für Strings zu verwenden.</p>
|
|
<h2 id="03_coding_style-6-formatierung">6. Formatierung</h2>
|
|
<p>Code ist sinnvoll Formatiert mit Einschüben etc.
|
|
Im Regelfall unterstützt VSCode dies Automatisch. Machen Sie Gebrauch von der
|
|
automatischen Formatierungsfunktion.</p>
|
|
<ul>
|
|
<li><a href="https://www.jetbrains.com/help/idea/reformat-and-rearrange-code.html#reformat_file">Anleitung für IntelliJ</a></li>
|
|
<li><a href="https://stackoverflow.com/questions/29973357/how-do-you-format-code-in-visual-studio-code-vscode">Anleitung für Visual Studio Code</a></li>
|
|
<li><a href="https://praxistipps.chip.de/eclipse-autoformat-code-so-gehts_98369">Anleitung für Eclipse</a></li>
|
|
</ul>
|
|
<h2 id="03_coding_style-8-magische-zahlen">8. "Magische" Zahlen</h2>
|
|
<p>Der Gebrauch von "magischen" Zahlen sollte vermieden werden. Solange es nicht
|
|
extrem offensichtlich ist, wofür eine Zahl
|
|
steht (z.B. <code>Math.pow(x, 5)</code>), sollte eine Variable (nach den oben genannten
|
|
Guidelines) angelegt werden, welcher die
|
|
Zahl als Wert zugewiesen wird. So entsteht der Zusammenhang zwischen der
|
|
Variablen und ihrer Bedeutung, und der Wert
|
|
kann an einer zentralen Stelle angepasst werden.</p>
|
|
<h2 id="03_coding_style-9-dateinamen-und-aufteilung">9. Dateinamen und -aufteilung</h2>
|
|
<p>Dateinamen dürfen keine Leerzeichen oder Umlaute enthalten, sind sonst aber frei
|
|
wählbar (s.u. für Einschränkungen). Es
|
|
wird empfohlen, die Zeichenwahl auf a-z, A-Z, 0-9 und _ zu beschränken.<br />
|
|
Code kann auf mehrere Dateien aufgeteilt werden, sofern dies sinnvoll
|
|
erscheint (z.B. um eine Trennung von Funktion und
|
|
Daten zu erreichen). Wenn Klassen verwendet werden, sollte jede ihre eigene
|
|
Datei bekommen. Sofern eine Datei eine
|
|
bestimmte Klasse enthält, soll die Datei mit dem Namen der Klasse benannt sein.</p>
|
|
<h2 id="03_coding_style-10-wiederholungen-sind-schlecht">10. Wiederholungen sind schlecht</h2>
|
|
<p>Code der sich ohne oder nur mit minimalen Änderungen wiederholt, kann in den
|
|
allermeisten Fällen besser geschrieben
|
|
werden, z.B. über eine Funktion mit Übergabeparametern, oder indem man nur den
|
|
geänderten Teil implementiert oder
|
|
überschreibt, während der Rest für alles gleich generiert wird.<br />
|
|
Dies hat viele Vorteile: Es macht den Code generell übersichtlicher (und damit
|
|
besser verständlich), kürzer, und
|
|
wartungsfreundlicher.</p></section><section class="print-page" id="04_introduction_to_objects"><h1 id="04_introduction_to_objects-04-einfuhrung-in-objekte">04: Einführung in Objekte</h1>
|
|
<h2 id="04_introduction_to_objects-kurze-begriffserklarung">Kurze Begriffserklärung</h2>
|
|
<p>Quelle: <a href="https://stackhowto.com/difference-between-instantiating-declaring-and-initializing/">stackhowto.com</a></p>
|
|
<h3 id="04_introduction_to_objects-declaration">Declaration</h3>
|
|
<blockquote>
|
|
<p>Declaring a variable means the first “mention” of the variable, which tells the compiler “Hello, I am here and can be used”.
|
|
In a statically typed language like Java, this also means that the declared type of the variable is determined.
|
|
The value itself is not determined during the declaration.
|
|
<div class="highlight"><pre><span></span><code><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="p">;</span><span class="w"></span>
|
|
<span class="kt">int</span><span class="w"> </span><span class="n">nbr</span><span class="p">;</span><span class="w"></span>
|
|
</code></pre></div></p>
|
|
</blockquote>
|
|
<h3 id="04_introduction_to_objects-initialization">Initialization</h3>
|
|
<blockquote>
|
|
<p>The term initialization usually means the first assignment of a value to a variable.
|
|
<div class="highlight"><pre><span></span><code><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">"Thomas"</span><span class="p">;</span><span class="w"></span>
|
|
<span class="kt">int</span><span class="w"> </span><span class="n">nbr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">5</span><span class="p">;</span><span class="w"></span>
|
|
</code></pre></div></p>
|
|
</blockquote>
|
|
<h3 id="04_introduction_to_objects-instantiation">Instantiation</h3>
|
|
<blockquote>
|
|
<p>The term instantiation actually has nothing to do with assigning a value to a variable, even if a new object is sometimes instantiated when a variable is initialized.
|
|
The term simply means the creation of a new object, i.e. an instance, from a class.
|
|
<div class="highlight"><pre><span></span><code><span class="n">String</span><span class="w"> </span><span class="n">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">String</span><span class="p">(</span><span class="s">"Thomas"</span><span class="p">);</span><span class="w"></span>
|
|
</code></pre></div></p>
|
|
</blockquote>
|
|
<h2 id="04_introduction_to_objects-1-einfache-objekte-und-veerbung">#1 Einfache Objekte und Veerbung</h2>
|
|
<p><strong>Lernziele:</strong>
|
|
* eine Klasse erzeugen
|
|
* eine Klasse aufrufen
|
|
* einfache Veerbung
|
|
* Polymorphie (Überschreiben von Methoden)
|
|
* die Verwendung von <code>this</code>
|
|
* die Verwendung von <code>super</code></p>
|
|
<div class="highlight"><pre><span></span><code><span class="c1">// main.java</span><span class="w"></span>
|
|
<span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Main</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">Animal</span><span class="w"> </span><span class="n">myAnimal</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Animal</span><span class="p">();</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">myAnimal</span><span class="p">.</span><span class="na">makeSound</span><span class="p">();</span><span class="w"></span>
|
|
|
|
<span class="w"> </span><span class="n">Dog</span><span class="w"> </span><span class="n">myDog</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Dog</span><span class="p">();</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">myDog</span><span class="p">.</span><span class="na">makeSound</span><span class="p">();</span><span class="w"></span>
|
|
|
|
<span class="w"> </span><span class="n">Cat</span><span class="w"> </span><span class="n">myCat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Cat</span><span class="p">();</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">myCat</span><span class="p">.</span><span class="na">makeSound</span><span class="p">();</span><span class="w"></span>
|
|
|
|
<span class="w"> </span><span class="n">myCat</span><span class="p">.</span><span class="na">compareToAnimal</span><span class="p">();</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
<span class="p">}</span><span class="w"></span>
|
|
</code></pre></div>
|
|
<div class="highlight"><pre><span></span><code><span class="c1">// Animal.java</span><span class="w"></span>
|
|
<span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Animal</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="n">isPet</span><span class="p">;</span><span class="w"></span>
|
|
|
|
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="nf">Animal</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"## in constructor of Animal"</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">isPet</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w"> </span><span class="c1">// it doesn't exist for our cats or dogs</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
|
|
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">makeSound</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"Yes, animal usually make sounds"</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
|
|
<span class="p">}</span><span class="w"></span>
|
|
</code></pre></div>
|
|
<p><div class="highlight"><pre><span></span><code><span class="c1">// Cat.java</span><span class="w"></span>
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|
<span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Cat</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Animal</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
|
|
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="nf">Cat</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"## in constructor of Cat"</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">isPet</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
|
|
<span class="w"> </span><span class="nd">@Override</span><span class="w"></span>
|
|
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">makeSound</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"meow meow"</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
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|
|
|
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">compareToAnimal</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"--- Animal ---"</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="kd">super</span><span class="p">.</span><span class="na">makeSound</span><span class="p">();</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"is alive: "</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="kd">super</span><span class="p">.</span><span class="na">isPet</span><span class="p">);</span><span class="w"></span>
|
|
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"--- Cat ---"</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">makeSound</span><span class="p">();</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"is alive: "</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">isPet</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
<span class="p">}</span><span class="w"></span>
|
|
</code></pre></div>
|
|
<div class="highlight"><pre><span></span><code><span class="c1">// Dog.java</span><span class="w"></span>
|
|
<span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Dog</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Animal</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
|
|
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="nf">Dog</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"## in constructor of Dog"</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">isPet</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
|
|
<span class="w"> </span><span class="nd">@Override</span><span class="w"></span>
|
|
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">makeSound</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"woof woof"</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">isPet</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
|
|
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">compareToAnimal</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"--- Animal ---"</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="kd">super</span><span class="p">.</span><span class="na">makeSound</span><span class="p">();</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"is alive: "</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="kd">super</span><span class="p">.</span><span class="na">isPet</span><span class="p">);</span><span class="w"></span>
|
|
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"--- Cat ---"</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">makeSound</span><span class="p">();</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"is alive: "</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">isPet</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
|
|
<span class="p">}</span><span class="w"></span>
|
|
</code></pre></div></p>
|
|
<h2 id="04_introduction_to_objects-2-komplexere-vererbung-von-klassen">#2 komplexere Vererbung von Klassen</h2>
|
|
<p><strong>Lernziele:</strong>
|
|
* Erweiterte Veerbung
|
|
* Modifikatoren für Attribute
|
|
* Getter und Setter
|
|
* Konstruktorverkettung</p>
|
|
<div class="highlight"><pre><span></span><code><span class="c1">// main.java</span><span class="w"></span>
|
|
<span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Main</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">Vehicle</span><span class="w"> </span><span class="n">myVehicle</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Vehicle</span><span class="p">();</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"-- myVehicle:"</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"number of wheels: "</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">myVehicle</span><span class="p">.</span><span class="na">getNumberOfWheels</span><span class="p">());</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"max Speed: "</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">myVehicle</span><span class="p">.</span><span class="na">getMaxSpeed</span><span class="p">());</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">myVehicle</span><span class="p">.</span><span class="na">setMaxSpeed</span><span class="p">(</span><span class="mi">150</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"max Speed: "</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">myVehicle</span><span class="p">.</span><span class="na">getMaxSpeed</span><span class="p">());</span><span class="w"></span>
|
|
|
|
<span class="w"> </span><span class="n">Car</span><span class="w"> </span><span class="n">myCar</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Car</span><span class="p">(</span><span class="s">"blue"</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"-- myCar:"</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"number of wheels: "</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">myCar</span><span class="p">.</span><span class="na">getNumberOfWheels</span><span class="p">());</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"max Speed: "</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">myCar</span><span class="p">.</span><span class="na">getMaxSpeed</span><span class="p">());</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">myVehicle</span><span class="p">.</span><span class="na">setMaxSpeed</span><span class="p">(</span><span class="mi">150</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"max Speed: "</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">myCar</span><span class="p">.</span><span class="na">getMaxSpeed</span><span class="p">());</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
<span class="p">}</span><span class="w"></span>
|
|
</code></pre></div>
|
|
<div class="highlight"><pre><span></span><code><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Vehicle</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="kd">protected</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">numberOfWheels</span><span class="p">;</span><span class="w"></span>
|
|
<span class="w"> </span><span class="kd">protected</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">maxSpeed</span><span class="p">;</span><span class="w"></span>
|
|
|
|
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="nf">Vehicle</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"## in default constructor of Vehicle"</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">numberOfWheels</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">4</span><span class="p">;</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">maxSpeed</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">100</span><span class="p">;</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
|
|
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="nf">Vehicle</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">numberOfWheels</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">maxSpeed</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"## in constructor of Vehicle"</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">numberOfWheels</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">numberOfWheels</span><span class="p">;</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">maxSpeed</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">maxSpeed</span><span class="p">;</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
|
|
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">getNumberOfWheels</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">numberOfWheels</span><span class="p">;</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
|
|
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">getMaxSpeed</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">maxSpeed</span><span class="p">;</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
|
|
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">printMaxSpeed</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">maxSpeed</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">" km/h"</span><span class="p">;</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
|
|
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setMaxSpeed</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">newMaxSpeed</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">newMaxSpeed</span><span class="w"> </span><span class="o"><</span><span class="w"> </span><span class="mi">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">return</span><span class="p">;</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">maxSpeed</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">newMaxSpeed</span><span class="p">;</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
|
|
<span class="p">}</span><span class="w"></span>
|
|
</code></pre></div>
|
|
<div class="highlight"><pre><span></span><code><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Car</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Vehicle</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">color</span><span class="p">;</span><span class="w"></span>
|
|
|
|
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="nf">Car</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">color</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="kd">super</span><span class="p">(</span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="mi">200</span><span class="p">);</span><span class="w"> </span><span class="c1">// always needs to be the first statement</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"## in constructor of Car"</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">color</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">color</span><span class="p">;</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
|
|
<span class="w"> </span><span class="nd">@Override</span><span class="w"></span>
|
|
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setMaxSpeed</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">newMaxSpeed</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">newMaxSpeed</span><span class="w"> </span><span class="o"><</span><span class="w"> </span><span class="mi">1000</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"No car shall be this slow tbh"</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">return</span><span class="p">;</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">maxSpeed</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">newMaxSpeed</span><span class="p">;</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
<span class="p">}</span><span class="w"></span>
|
|
</code></pre></div>
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|
<div class="highlight"><pre><span></span><code><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Car</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Vehicle</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
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|
<span class="w"> </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">color</span><span class="p">;</span><span class="w"></span>
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|
|
|
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="nf">Car</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">color</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="kd">super</span><span class="p">(</span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="mi">200</span><span class="p">);</span><span class="w"> </span><span class="c1">// always needs to be the first statement</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"## in constructor of Car"</span><span class="p">);</span><span class="w"></span>
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|
<span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">color</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">color</span><span class="p">;</span><span class="w"></span>
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<span class="w"> </span><span class="p">}</span><span class="w"></span>
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|
|
<span class="w"> </span><span class="nd">@Override</span><span class="w"></span>
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|
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setMaxSpeed</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">newMaxSpeed</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">newMaxSpeed</span><span class="w"> </span><span class="o"><</span><span class="w"> </span><span class="mi">1000</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"No car shall be this slow tbh"</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">return</span><span class="p">;</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">maxSpeed</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">newMaxSpeed</span><span class="p">;</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
<span class="p">}</span><span class="w"></span>
|
|
</code></pre></div>
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|
<div class="highlight"><pre><span></span><code><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Truck</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Vehicle</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="kd">private</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="n">isFireTruck</span><span class="p">;</span><span class="w"></span>
|
|
<span class="w"> </span><span class="kd">private</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">hornSound</span><span class="p">;</span><span class="w"></span>
|
|
|
|
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="nf">Truck</span><span class="p">(</span><span class="kt">boolean</span><span class="w"> </span><span class="n">isFireTruck</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="kd">super</span><span class="p">(</span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="mi">200</span><span class="p">);</span><span class="w"> </span><span class="c1">// always needs to be the first statement</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"## in constructor of Truck"</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">isFireTruck</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">isFireTruck</span><span class="p">;</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">hornSound</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">"test"</span><span class="p">;</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
|
|
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">getIsFireTruck</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">isFireTruck</span><span class="p">;</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
<span class="p">}</span><span class="w"></span>
|
|
</code></pre></div>
|
|
<h2 id="04_introduction_to_objects-3-static-in-einer-klasse">#3 <code>static</code> in einer Klasse</h2>
|
|
<p><strong>Lernziele:</strong>
|
|
* statische und dynamische Variablen
|
|
* statische und dynamische Methoden</p>
|
|
<div class="highlight"><pre><span></span><code><span class="c1">// main.java</span><span class="w"></span>
|
|
<span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Main</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">Counter</span><span class="p">.</span><span class="na">printCounterStatic</span><span class="p">(</span><span class="s">"Static"</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">Counter</span><span class="p">.</span><span class="na">increaseCounterStatic</span><span class="p">();</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">Counter</span><span class="p">.</span><span class="na">printCounterStatic</span><span class="p">(</span><span class="s">"Static"</span><span class="p">);</span><span class="w"></span>
|
|
|
|
<span class="w"> </span><span class="n">Counter</span><span class="w"> </span><span class="n">myCounter</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Counter</span><span class="p">();</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">Counter</span><span class="p">.</span><span class="na">increaseCounterStatic</span><span class="p">();</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">myCounter</span><span class="p">.</span><span class="na">increaseCounterDynamic</span><span class="p">();</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">myCounter</span><span class="p">.</span><span class="na">printCounterDynamic</span><span class="p">(</span><span class="s">"Dynamic"</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
<span class="p">}</span><span class="w"></span>
|
|
</code></pre></div>
|
|
<div class="highlight"><pre><span></span><code><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Counter</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">counterValueStatic</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span><span class="w"></span>
|
|
<span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">counterValueDynamic</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span><span class="w"></span>
|
|
|
|
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">increaseCounterStatic</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">counterValueStatic</span><span class="o">++</span><span class="p">;</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
|
|
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">increaseCounterDynamic</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">counterValueDynamic</span><span class="o">++</span><span class="p">;</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
|
|
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">printCounterDynamic</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">classID</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">">> execute printCounterDynamic of class "</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">classID</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"static: "</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">counterValueStatic</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"dynamic: "</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">counterValueDynamic</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
|
|
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">printCounterStatic</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">classID</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">">> execute printCounterStatic of class "</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">classID</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"dynamic: "</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">counterValueStatic</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
<span class="p">}</span><span class="w"></span>
|
|
</code></pre></div></section><section class="print-page" id="05_types_of_objects"><h1 id="05_types_of_objects-05-typen-von-objekten">05: Typen von Objekten</h1>
|
|
<h2 id="05_types_of_objects-enumerations">Enumerations</h2>
|
|
<div class="highlight"><pre><span></span><code><span class="c1">// SecurityLevel.java</span><span class="w"></span>
|
|
<span class="kd">public</span><span class="w"> </span><span class="kd">enum</span><span class="w"> </span><span class="n">SecurityLevel</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">LOW</span><span class="p">,</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">MEDIUM</span><span class="p">,</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">HIGH</span><span class="p">;</span><span class="w"></span>
|
|
<span class="p">}</span><span class="w"></span>
|
|
</code></pre></div>
|
|
<div class="highlight"><pre><span></span><code><span class="c1">// Main.java</span><span class="w"></span>
|
|
<span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Main</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">SecurityLevel</span><span class="w"> </span><span class="n">networkSecurity</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">SecurityLevel</span><span class="p">.</span><span class="na">MEDIUM</span><span class="p">;</span><span class="w"></span>
|
|
|
|
<span class="w"> </span><span class="c1">// comparing enum items</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">networkSecurity</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">SecurityLevel</span><span class="p">.</span><span class="na">HIGH</span><span class="p">);</span><span class="w"> </span><span class="c1">// false</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">networkSecurity</span><span class="p">.</span><span class="na">compareTo</span><span class="p">(</span><span class="n">SecurityLevel</span><span class="p">.</span><span class="na">LOW</span><span class="p">));</span><span class="w"> </span><span class="c1">// 1</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">networkSecurity</span><span class="p">.</span><span class="na">compareTo</span><span class="p">(</span><span class="n">SecurityLevel</span><span class="p">.</span><span class="na">MEDIUM</span><span class="p">));</span><span class="w"> </span><span class="c1">// 0</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">networkSecurity</span><span class="p">.</span><span class="na">compareTo</span><span class="p">(</span><span class="n">SecurityLevel</span><span class="p">.</span><span class="na">HIGH</span><span class="p">));</span><span class="w"> </span><span class="c1">// -1</span><span class="w"></span>
|
|
|
|
<span class="w"> </span><span class="c1">// print all possible values</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">for</span><span class="p">(</span><span class="n">SecurityLevel</span><span class="w"> </span><span class="n">value</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">SecurityLevel</span><span class="p">.</span><span class="na">values</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">value</span><span class="p">.</span><span class="na">ordinal</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">" "</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">value</span><span class="p">.</span><span class="na">name</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">" "</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">value</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
|
|
<span class="w"> </span><span class="k">switch</span><span class="w"> </span><span class="p">(</span><span class="n">networkSecurity</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">case</span><span class="w"> </span><span class="n">LOW</span><span class="p">:</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"The network security MUST be increased!"</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">break</span><span class="p">;</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">case</span><span class="w"> </span><span class="n">MEDIUM</span><span class="p">:</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"The network security needs improvements"</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">break</span><span class="p">;</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">case</span><span class="w"> </span><span class="n">HIGH</span><span class="p">:</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"The network security is good so far"</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">break</span><span class="p">;</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
<span class="p">}</span><span class="w"></span>
|
|
</code></pre></div>
|
|
<h2 id="05_types_of_objects-generics">Generics</h2>
|
|
<div class="highlight"><pre><span></span><code><span class="c1">// Main.java</span><span class="w"></span>
|
|
<span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Main</span><span class="w"> </span><span class="cm">/*extends Language implements Regex*/</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
|
|
<span class="w"> </span><span class="n">SaveState</span><span class="o"><</span><span class="n">String</span><span class="o">></span><span class="w"> </span><span class="n">stateFirst</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">SaveState</span><span class="o"><</span><span class="n">String</span><span class="o">></span><span class="p">(</span><span class="s">"Begin of the story"</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">SaveState</span><span class="o"><</span><span class="n">String</span><span class="o">></span><span class="w"> </span><span class="n">stateSecond</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">SaveState</span><span class="o"><</span><span class="n">String</span><span class="o">></span><span class="p">(</span><span class="s">"Near last boss fight"</span><span class="p">);</span><span class="w"></span>
|
|
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">stateFirst</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">stateSecond</span><span class="p">);</span><span class="w"></span>
|
|
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"second state bigger? "</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">stateSecond</span><span class="p">.</span><span class="na">compareTo</span><span class="p">(</span><span class="n">stateFirst</span><span class="p">));</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"first state bigger? "</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">stateFirst</span><span class="p">.</span><span class="na">compareTo</span><span class="p">(</span><span class="n">stateSecond</span><span class="p">));</span><span class="w"></span>
|
|
|
|
<span class="w"> </span><span class="n">stateFirst</span><span class="p">.</span><span class="na">setSaveState</span><span class="p">(</span><span class="s">"Finished tutorial"</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">stateFirst</span><span class="p">.</span><span class="na">getSaveState</span><span class="p">());</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
<span class="p">}</span><span class="w"></span>
|
|
</code></pre></div>
|
|
<h3 id="05_types_of_objects-abstract-and-interface">Abstract and Interface</h3>
|
|
<p><div class="highlight"><pre><span></span><code><span class="c1">// Regex.java</span><span class="w"></span>
|
|
<span class="kd">public</span><span class="w"> </span><span class="kd">interface</span> <span class="nc">Regex</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">concatStrings</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">left</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">right</span><span class="p">);</span><span class="w"></span>
|
|
<span class="p">}</span><span class="w"></span>
|
|
</code></pre></div>
|
|
<div class="highlight"><pre><span></span><code><span class="c1">// Main.java</span><span class="w"></span>
|
|
<span class="kd">abstract</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Language</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">showLanguage</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"This text is presented to you by Java"</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="kd">abstract</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">sayHelloWorld</span><span class="p">();</span><span class="w"></span>
|
|
<span class="p">}</span><span class="w"></span>
|
|
|
|
<span class="c1">// Main.java</span><span class="w"></span>
|
|
<span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Main</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Language</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Regex</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="c1">// Language myLanguage = new Language();</span><span class="w"></span>
|
|
<span class="w"> </span><span class="c1">// 'Language' is abstract; cannot be instantiated</span><span class="w"></span>
|
|
|
|
<span class="w"> </span><span class="n">Main</span><span class="w"> </span><span class="n">myObject</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Main</span><span class="p">();</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">myObject</span><span class="p">.</span><span class="na">sayHelloWorld</span><span class="p">();</span><span class="w"></span>
|
|
|
|
<span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">wortwitz</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">myObject</span><span class="p">.</span><span class="na">concatStrings</span><span class="p">(</span><span class="s">"du"</span><span class="p">,</span><span class="w"> </span><span class="s">"schlampe"</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">wortwitz</span><span class="p">);</span><span class="w"> </span><span class="c1">// duschlampe</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
|
|
<span class="w"> </span><span class="nd">@Override</span><span class="w"></span>
|
|
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">sayHelloWorld</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"I refuse to say that!"</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
|
|
<span class="w"> </span><span class="nd">@Override</span><span class="w"></span>
|
|
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">concatStrings</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">left</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">right</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n">left</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">right</span><span class="p">;</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
<span class="p">}</span><span class="w"></span>
|
|
</code></pre></div>
|
|
<div class="highlight"><pre><span></span><code><span class="c1">// SaveState.java</span><span class="w"></span>
|
|
|
|
<span class="kn">import</span><span class="w"> </span><span class="nn">java.security.InvalidParameterException</span><span class="p">;</span><span class="w"></span>
|
|
|
|
<span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">SaveState</span><span class="o"><</span><span class="n">T</span><span class="o">></span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">Comparable</span><span class="o"><</span><span class="n">SaveState</span><span class="o">></span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="kd">private</span><span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="n">saveEntry</span><span class="p">;</span><span class="w"></span>
|
|
<span class="w"> </span><span class="kd">private</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">saveID</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span><span class="w"></span>
|
|
<span class="w"> </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">staticSaveID</span><span class="p">;</span><span class="w"></span>
|
|
|
|
<span class="w"> </span><span class="c1">// constructor</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">SaveState</span><span class="p">(</span><span class="n">T</span><span class="w"> </span><span class="n">saveEntry</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">InvalidParameterException</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">if</span><span class="p">(</span><span class="n">saveEntry</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">InvalidParameterException</span><span class="p">(</span><span class="s">"entry shall not be null"</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">saveEntry</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">saveEntry</span><span class="p">;</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">saveID</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">staticSaveID</span><span class="p">;</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">staticSaveID</span><span class="o">++</span><span class="p">;</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
|
|
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">getSaveID</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">saveID</span><span class="p">;</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
|
|
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="nf">getSaveState</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">saveEntry</span><span class="p">;</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
|
|
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">setSaveState</span><span class="p">(</span><span class="n">T</span><span class="w"> </span><span class="n">saveEntry</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">InvalidParameterException</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">if</span><span class="p">(</span><span class="n">saveEntry</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">InvalidParameterException</span><span class="p">(</span><span class="s">"entry shall not be null"</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">saveEntry</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">saveEntry</span><span class="p">;</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
|
|
<span class="w"> </span><span class="nd">@Override</span><span class="w"></span>
|
|
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">toString</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">saveID</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">": "</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">saveEntry</span><span class="p">.</span><span class="na">toString</span><span class="p">();</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">Exception</span><span class="w"> </span><span class="n">exception</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"T.toString() for Class "</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">saveEntry</span><span class="p">.</span><span class="na">getClass</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">" does not exist"</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
|
|
<span class="w"> </span><span class="nd">@Override</span><span class="w"></span>
|
|
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">compareTo</span><span class="p">(</span><span class="n">SaveState</span><span class="w"> </span><span class="n">object</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">saveID</span><span class="w"> </span><span class="o">></span><span class="w"> </span><span class="n">object</span><span class="p">.</span><span class="na">getSaveID</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">this</span><span class="p">.</span><span class="na">saveID</span><span class="w"> </span><span class="o"><</span><span class="w"> </span><span class="n">object</span><span class="p">.</span><span class="na">getSaveID</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="o">-</span><span class="mi">1</span><span class="p">;</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
<span class="p">}</span><span class="w"></span>
|
|
</code></pre></div></p>
|
|
<h2 id="05_types_of_objects-collections">Collections</h2>
|
|
<div class="highlight"><pre><span></span><code><span class="kn">import</span><span class="w"> </span><span class="nn">java.util.*</span><span class="p">;</span><span class="w"></span>
|
|
|
|
<span class="c1">// Main.java</span><span class="w"></span>
|
|
<span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Main</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
|
|
<span class="w"> </span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">alphabet</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="s">"bee"</span><span class="p">,</span><span class="w"></span>
|
|
<span class="w"> </span><span class="s">"apple"</span><span class="p">,</span><span class="w"></span>
|
|
<span class="w"> </span><span class="s">"clown"</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">};</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="w"> </span><span class="n">Arrays</span><span class="p">.</span><span class="na">toString</span><span class="p">(</span><span class="n">alphabet</span><span class="p">)</span><span class="w"> </span><span class="p">);</span><span class="w"></span>
|
|
|
|
<span class="w"> </span><span class="n">ArrayList</span><span class="o"><</span><span class="n">String</span><span class="o">></span><span class="w"> </span><span class="n">myArrayList</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrayList</span><span class="o"><</span><span class="n">String</span><span class="o">></span><span class="p">();</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">TreeSet</span><span class="o"><</span><span class="n">String</span><span class="o">></span><span class="w"> </span><span class="n">myTreeSet</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">TreeSet</span><span class="o"><</span><span class="n">String</span><span class="o">></span><span class="p">();</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">HashMap</span><span class="o"><</span><span class="n">Integer</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="o">></span><span class="w"> </span><span class="n">myHashMap</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HashMap</span><span class="o"><></span><span class="p">();</span><span class="w"></span>
|
|
|
|
<span class="w"> </span><span class="k">for</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">selection</span><span class="p">:</span><span class="w"> </span><span class="n">alphabet</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">myArrayList</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">selection</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">myTreeSet</span><span class="p">.</span><span class="na">add</span><span class="p">(</span><span class="n">selection</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">myHashMap</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="n">myHashMap</span><span class="p">.</span><span class="na">size</span><span class="p">(),</span><span class="w"> </span><span class="n">selection</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
|
|
<span class="w"> </span><span class="n">Set</span><span class="o"><</span><span class="n">Integer</span><span class="o">></span><span class="w"> </span><span class="n">mapKeys</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">myHashMap</span><span class="p">.</span><span class="na">keySet</span><span class="p">();</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">mapKeys</span><span class="p">);</span><span class="w"></span>
|
|
|
|
<span class="w"> </span><span class="n">Collection</span><span class="o"><</span><span class="n">String</span><span class="o">></span><span class="w"> </span><span class="n">mapValues</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">myHashMap</span><span class="p">.</span><span class="na">values</span><span class="p">();</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">mapValues</span><span class="p">);</span><span class="w"></span>
|
|
|
|
<span class="w"> </span><span class="n">Iterator</span><span class="o"><</span><span class="n">String</span><span class="o">></span><span class="w"> </span><span class="n">arrayListIterator</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">myArrayList</span><span class="p">.</span><span class="na">iterator</span><span class="p">();</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">Iterator</span><span class="o"><</span><span class="n">String</span><span class="o">></span><span class="w"> </span><span class="n">treeSetIterator</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">myTreeSet</span><span class="p">.</span><span class="na">iterator</span><span class="p">();</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">Iterator</span><span class="o"><</span><span class="n">String</span><span class="o">></span><span class="w"> </span><span class="n">hashMapIterator</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">myHashMap</span><span class="p">.</span><span class="na">values</span><span class="p">().</span><span class="na">iterator</span><span class="p">();</span><span class="w"></span>
|
|
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"--- arrayList ---"</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">selectedValue</span><span class="p">:</span><span class="w"> </span><span class="n">myArrayList</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">selectedValue</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"--- arrayListIterator ---"</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">arrayListIterator</span><span class="p">.</span><span class="na">hasNext</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">arrayListIterator</span><span class="p">.</span><span class="na">next</span><span class="p">());</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"--- treeSet ---"</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">selectedValue</span><span class="p">:</span><span class="w"> </span><span class="n">myTreeSet</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">ystem</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">selectedValue</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"--- treeSetIterator ---"</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">treeSetIterator</span><span class="p">.</span><span class="na">hasNext</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">treeSetIterator</span><span class="p">.</span><span class="na">next</span><span class="p">());</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"--- hashMap ---"</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">Map</span><span class="p">.</span><span class="na">Entry</span><span class="o"><</span><span class="n">Integer</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="o">></span><span class="w"> </span><span class="n">pair</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">myHashMap</span><span class="p">.</span><span class="na">entrySet</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">pair</span><span class="p">.</span><span class="na">getKey</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">": "</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">pair</span><span class="p">.</span><span class="na">getValue</span><span class="p">());</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"--- hashMapIterator ---"</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">hashMapIterator</span><span class="p">.</span><span class="na">hasNext</span><span class="p">())</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="n">hashMapIterator</span><span class="p">.</span><span class="na">next</span><span class="p">());</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
<span class="p">}</span><span class="w"></span>
|
|
</code></pre></div>
|
|
<ul>
|
|
<li>List - für beliebig große Listen, deren Elemente auch über einen Index zugegriffen werden können,<ul>
|
|
<li><code>ArrayList</code> - Indizierte Liste, deren Größe dynamisch verändert werden kann. Indexzugriffe sind schnell, Größenänderungen sind aufwändig.</li>
|
|
<li><code>LinkedList</code> - Verkettete Liste. Indexzugriffe sind langsam, Einfügen und Löschen ist schnell.</li>
|
|
</ul>
|
|
</li>
|
|
<li>Set - zur Darstellung von Mengen<ul>
|
|
<li><code>HashSet</code> - ungeordnete Datenmenge (ohne Duplikate)</li>
|
|
<li><code>TreeSet</code> - Sortierte Menge.</li>
|
|
</ul>
|
|
</li>
|
|
<li>Map - für Paare von Daten verschiedenen Typs.<ul>
|
|
<li><code>HashMap</code> - Menge von (Schlüssel,Wert)-Paaren</li>
|
|
<li><code>TreeMap</code> - nach Schlüsseln sortierte Menge von (Schlüssel,Wert)-Paaren</li>
|
|
</ul>
|
|
</li>
|
|
</ul>
|
|
<h3 id="05_types_of_objects-collection-interface-list-set-map">Collection Interface (List, Set, Map)</h3>
|
|
<table>
|
|
<thead>
|
|
<tr>
|
|
<th>Methode</th>
|
|
<th>Beschreibung</th>
|
|
</tr>
|
|
</thead>
|
|
<tbody>
|
|
<tr>
|
|
<td>int size()</td>
|
|
<td>liefert die Anzahl der Einträge</td>
|
|
</tr>
|
|
<tr>
|
|
<td>boolean isEmpty()</td>
|
|
<td>prüft, ob keine Einträge vorhanden sind</td>
|
|
</tr>
|
|
<tr>
|
|
<td>boolean contains(Object o)</td>
|
|
<td>prüft, ob o eingetragen ist</td>
|
|
</tr>
|
|
<tr>
|
|
<td>boolean add(Object o)</td>
|
|
<td>prüft, ob alle Elemente aus c enthalten sind</td>
|
|
</tr>
|
|
<tr>
|
|
<td>boolean addAll(Collection c)</td>
|
|
<td>trägt alle Elemente aus c ein (optional)</td>
|
|
</tr>
|
|
<tr>
|
|
<td>boolean remove(Object o)</td>
|
|
<td>entfernt o (optional)</td>
|
|
</tr>
|
|
<tr>
|
|
<td>boolean removeAll(Collection c)</td>
|
|
<td>entfernt die in c angegebenen Elemente (optional)</td>
|
|
</tr>
|
|
<tr>
|
|
<td>boolean retainAll(Collection c)</td>
|
|
<td>entfernt alle Elemente, außer die in c angegebenen (optional)</td>
|
|
</tr>
|
|
<tr>
|
|
<td>boolean equals(Object o)</td>
|
|
<td>prüft, ob o mit der Collection übereinstimmt</td>
|
|
</tr>
|
|
<tr>
|
|
<td>Iterator iterator()</td>
|
|
<td>erzeugt einen Iterator</td>
|
|
</tr>
|
|
<tr>
|
|
<td>void clear()</td>
|
|
<td>entfernt alle Elemente (optional)</td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<h3 id="05_types_of_objects-list-interface">List Interface</h3>
|
|
<table>
|
|
<thead>
|
|
<tr>
|
|
<th>Methode</th>
|
|
<th>Beschreibung</th>
|
|
</tr>
|
|
</thead>
|
|
<tbody>
|
|
<tr>
|
|
<td>Object get(int i)</td>
|
|
<td>liefert das Element an Position i (ohne es zu entfernen)</td>
|
|
</tr>
|
|
<tr>
|
|
<td>int indexOf(Object o)</td>
|
|
<td>liefert den Index des ersten Vorkommens von o oder -1</td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<h3 id="05_types_of_objects-map-interface">Map Interface</h3>
|
|
<table>
|
|
<thead>
|
|
<tr>
|
|
<th>Methode</th>
|
|
<th>Beschreibung</th>
|
|
</tr>
|
|
</thead>
|
|
<tbody>
|
|
<tr>
|
|
<td>boolean containsKey(Object key)</td>
|
|
<td>prüft, ob ein Datenpaar mit Schlüssel key eingetragen ist</td>
|
|
</tr>
|
|
<tr>
|
|
<td>boolean containsValue(Object value)</td>
|
|
<td>prüft, ob ein Datenpaar mit Wert value eingetragen ist</td>
|
|
</tr>
|
|
<tr>
|
|
<td>Object get(Object key)</td>
|
|
<td>liefert den eingetragenen Wert zum Schlüssen key</td>
|
|
</tr>
|
|
<tr>
|
|
<td>Object put(Object key, Object value)</td>
|
|
<td>trägt das Datenpaar(key,value) ein (optional)</td>
|
|
</tr>
|
|
<tr>
|
|
<td>boolean remove(Object key)</td>
|
|
<td>entfernt das Datenpaar mit Schlüssel key (optional)</td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<h3 id="05_types_of_objects-iteratoren-list-set">Iteratoren (List, Set)</h3>
|
|
<table>
|
|
<thead>
|
|
<tr>
|
|
<th>Methode</th>
|
|
<th>Beschreibung</th>
|
|
</tr>
|
|
</thead>
|
|
<tbody>
|
|
<tr>
|
|
<td>boolean hasNext()</td>
|
|
<td>prüft, ob ein weiteres Element existiert</td>
|
|
</tr>
|
|
<tr>
|
|
<td>Object next()</td>
|
|
<td>liefert das nächste Element und schaltet weiter</td>
|
|
</tr>
|
|
<tr>
|
|
<td>void remove()</td>
|
|
<td>löscht das aktuelle Element</td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<h3 id="05_types_of_objects-listiterator-list">ListIterator (List)</h3>
|
|
<table>
|
|
<thead>
|
|
<tr>
|
|
<th>Methode</th>
|
|
<th>Beschreibung</th>
|
|
</tr>
|
|
</thead>
|
|
<tbody>
|
|
<tr>
|
|
<td>boolean hasPrevious()</td>
|
|
<td>prüft, ob ein Vorgänger existiert</td>
|
|
</tr>
|
|
<tr>
|
|
<td>Object previous()</td>
|
|
<td>liefert das vorherige Element</td>
|
|
</tr>
|
|
<tr>
|
|
<td>void add(Object o)</td>
|
|
<td>fügt ein neues Element o hinter dem aktuellen Element ein</td>
|
|
</tr>
|
|
<tr>
|
|
<td>void set(Object o)</td>
|
|
<td>ersetzt das aktuelle Element durch o</td>
|
|
</tr>
|
|
</tbody>
|
|
</table></section><section class="print-page" id="06_java_docs"><h1 id="06_java_docs-06-javadoc">06: JavaDoc</h1>
|
|
<p>Quelle: <a href="https://binfalse.de/2015/10/05/javadoc-cheats-sheet/">JavaDoc Cheatsheet</a></p>
|
|
<p>Output as PDF: <a href="https://github.com/YamiDoesDev/algodat-java-intro/blob/main/media/javadoc_main.pdf">JavaDoc from class Main</a></p>
|
|
<div class="highlight"><pre><span></span><code><span class="cm">/**</span>
|
|
<span class="cm"> * This is the Main class</span>
|
|
<span class="cm"> * @version 1.0.1</span>
|
|
<span class="cm"> * @author Justin Drtvic</span>
|
|
<span class="cm"> */</span><span class="w"></span>
|
|
<span class="c1">// Main.java</span><span class="w"></span>
|
|
<span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Main</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="cm">/**</span>
|
|
<span class="cm"> * this is the main function, which is needed to execute the code</span>
|
|
<span class="cm"> * @param args params passed by the command line</span>
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<span class="cm"> */</span><span class="w"></span>
|
|
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
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<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="w"> </span><span class="n">addition</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">)</span><span class="w"> </span><span class="p">);</span><span class="w"></span>
|
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<span class="w"> </span><span class="p">}</span><span class="w"></span>
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<span class="w"> </span><span class="cm">/**</span>
|
|
<span class="cm"> * addition of two integer numbers</span>
|
|
<span class="cm"> * @param left number for left side</span>
|
|
<span class="cm"> * @param right number for right side</span>
|
|
<span class="cm"> * @return sum of two numbers</span>
|
|
<span class="cm"> * @throws IllegalArgumentException for numbers smaller than 0</span>
|
|
<span class="cm"> * @see Math</span>
|
|
<span class="cm"> * @see <a href="https://www.mathebibel.de/addition/">Mathebibel Addition</a></span>
|
|
<span class="cm"> * @since Java API 7</span>
|
|
<span class="cm"> * @deprecated deprecated since 3.0.0</span>
|
|
<span class="cm"> */</span><span class="w"></span>
|
|
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="nf">addition</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">left</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">right</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">left</span><span class="w"> </span><span class="o"><</span><span class="w"> </span><span class="mi">0</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">right</span><span class="w"> </span><span class="o"><</span><span class="w"> </span><span class="mi">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">throw</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">IllegalArgumentException</span><span class="p">(</span><span class="s">"we don't like numbers smaller than 0"</span><span class="p">);</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
<span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n">left</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">right</span><span class="p">;</span><span class="w"></span>
|
|
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
|
<span class="p">}</span><span class="w"></span>
|
|
</code></pre></div></section></div>
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