1550 lines
86 KiB
HTML
1550 lines
86 KiB
HTML
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Zum Inhalt
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Markdown Docs
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02: Basics
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<div class="md-search-result" data-md-component="search-result">
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<div class="md-search-result__meta">
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Suche wird initialisiert
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</div>
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<ol class="md-search-result__list"></ol>
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</div>
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</div>
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</div>
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</div>
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<div class="md-header__source">
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<a href="https://github.com/YamiDoesDev/algodat-java-intro" title="Quellcode" class="md-source" data-md-component="source">
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<div class="md-source__icon md-icon">
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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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<div class="md-source__repository">
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GitHub
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</div>
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</a>
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</div>
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</nav>
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</header>
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<div class="md-container" data-md-component="container">
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<main class="md-main" data-md-component="main">
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<div class="md-main__inner md-grid">
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<div class="md-sidebar md-sidebar--primary" data-md-component="sidebar" data-md-type="navigation" >
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<div class="md-sidebar__scrollwrap">
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<nav class="md-nav md-nav--primary" aria-label="Navigation" data-md-level="0">
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<label class="md-nav__title" for="__drawer">
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<a href="index.html" title="Markdown Docs" class="md-nav__button md-logo" aria-label="Markdown Docs" data-md-component="logo">
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Markdown Docs
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<div class="md-nav__source">
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<a href="https://github.com/YamiDoesDev/algodat-java-intro" title="Quellcode" class="md-source" data-md-component="source">
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<div class="md-source__icon md-icon">
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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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<div class="md-source__repository">
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GitHub
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</a>
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<ul class="md-nav__list" data-md-scrollfix>
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<li class="md-nav__item">
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<a href="index.html" class="md-nav__link">
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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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<li class="md-nav__item">
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<a href="01_hello_world.html" class="md-nav__link">
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01: Hello World
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</a>
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<input class="md-nav__toggle md-toggle" data-md-toggle="toc" type="checkbox" id="__toc">
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<label class="md-nav__link md-nav__link--active" for="__toc">
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02: Basics
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<span class="md-nav__icon md-icon"></span>
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</label>
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<a href="02_basics.html" class="md-nav__link md-nav__link--active">
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02: Basics
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</a>
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<nav class="md-nav md-nav--secondary" aria-label="Inhaltsverzeichnis">
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<label class="md-nav__title" for="__toc">
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<span class="md-nav__icon md-icon"></span>
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Inhaltsverzeichnis
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</label>
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<ul class="md-nav__list" data-md-component="toc" data-md-scrollfix>
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<li class="md-nav__item">
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<a href="#table-of-contents" class="md-nav__link">
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Table of Contents
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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="#nutzung-der-konsole" class="md-nav__link">
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Nutzung der Konsole
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</a>
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<nav class="md-nav" aria-label="Nutzung der Konsole">
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<ul class="md-nav__list">
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<li class="md-nav__item">
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<a href="#ausgabe" class="md-nav__link">
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Ausgabe
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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="#eingabe" class="md-nav__link">
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Eingabe
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</a>
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</li>
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</ul>
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</nav>
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</li>
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<li class="md-nav__item">
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<a href="#primitive-datentypen" class="md-nav__link">
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Primitive Datentypen
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</a>
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<nav class="md-nav" aria-label="Primitive Datentypen">
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<ul class="md-nav__list">
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<li class="md-nav__item">
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<a href="#type-casting" class="md-nav__link">
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Type Casting
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</a>
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<nav class="md-nav" aria-label="Type Casting">
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<ul class="md-nav__list">
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<li class="md-nav__item">
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<a href="#widening-casting-automatically" class="md-nav__link">
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Widening Casting (automatically)
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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="#narrowing-casting-manually" class="md-nav__link">
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Narrowing Casting (manually)
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</a>
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</li>
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</ul>
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</nav>
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</li>
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</ul>
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</nav>
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</li>
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<li class="md-nav__item">
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<a href="#nicht-primitive-datentypen" class="md-nav__link">
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Nicht Primitive Datentypen
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</a>
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<nav class="md-nav" aria-label="Nicht Primitive Datentypen">
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<ul class="md-nav__list">
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<li class="md-nav__item">
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<a href="#string" class="md-nav__link">
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String
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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="#numeric-datatypes" class="md-nav__link">
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Numeric Datatypes
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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="#arrays" class="md-nav__link">
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Arrays
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</a>
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</li>
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</ul>
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</nav>
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</li>
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<li class="md-nav__item">
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<a href="#operatoren" class="md-nav__link">
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Operatoren
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</a>
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<nav class="md-nav" aria-label="Operatoren">
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<ul class="md-nav__list">
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<li class="md-nav__item">
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<a href="#arithmetic-operators" class="md-nav__link">
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Arithmetic Operators
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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="#comparison-operators" class="md-nav__link">
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Comparison Operators
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</a>
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</li>
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</ul>
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</nav>
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</li>
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<li class="md-nav__item">
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<a href="#bedingungen" class="md-nav__link">
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Bedingungen
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</a>
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<nav class="md-nav" aria-label="Bedingungen">
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<ul class="md-nav__list">
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<li class="md-nav__item">
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<a href="https://github.com/YamiDoesDev/algodat-java-intro/edit/main/docs/02_basics.md" title="Seite editieren" class="md-content__button md-icon">
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<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24"><path d="M20.71 7.04c.39-.39.39-1.04 0-1.41l-2.34-2.34c-.37-.39-1.02-.39-1.41 0l-1.84 1.83 3.75 3.75M3 17.25V21h3.75L17.81 9.93l-3.75-3.75L3 17.25Z"/></svg>
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<h1 id="02-basics">02: Basics</h1>
|
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<h2 id="table-of-contents">Table of Contents</h2>
|
|
<ol>
|
|
<li><a href="#nutzung-der-konsole">Nutzung der Konsole</a></li>
|
|
<li><a href="#primitive-datentypen">Primitive Datentypen</a></li>
|
|
<li><a href="#nicht-primitive-datentypen">Nicht Primitive Datentypen</a></li>
|
|
<li><a href="#operatoren">Operatoren</a></li>
|
|
<li><a href="#bedingungen">Bedingungen</a></li>
|
|
<li><a href="#schleifen">Schleifen</a></li>
|
|
<li><a href="#exceptions">Exceptions</a></li>
|
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</ol>
|
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<h2 id="nutzung-der-konsole">Nutzung der Konsole</h2>
|
|
<h3 id="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="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="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="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="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="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="nicht-primitive-datentypen">Nicht Primitive Datentypen</h2>
|
|
<h3 id="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:</p>
|
|
<table>
|
|
<thead>
|
|
<tr>
|
|
<th>Methode</th>
|
|
<th>Beschreibung</th>
|
|
</tr>
|
|
</thead>
|
|
<tbody>
|
|
<tr>
|
|
<td>myString.charAt()</td>
|
|
<td>Returns the char value at the specified index.</td>
|
|
</tr>
|
|
<tr>
|
|
<td>myString.indexOf()</td>
|
|
<td>Returns the index within this string of the first occurrence of the specified substring.</td>
|
|
</tr>
|
|
<tr>
|
|
<td>myString.substring()</td>
|
|
<td>Returns a string that is a substring of this string.</td>
|
|
</tr>
|
|
<tr>
|
|
<td>myString.equals()</td>
|
|
<td>Compares this string to the specified object.</td>
|
|
</tr>
|
|
<tr>
|
|
<td>myString.toLowerCase()</td>
|
|
<td>Converts all of the characters in this String to lower case.</td>
|
|
</tr>
|
|
<tr>
|
|
<td>myString.toUpperCase()</td>
|
|
<td>Converts all of the characters in this String to upper case.</td>
|
|
</tr>
|
|
<tr>
|
|
<td>myString.contains()</td>
|
|
<td>Returns true if and only if this string contains the specified sequence of char values.</td>
|
|
</tr>
|
|
<tr>
|
|
<td>myString.replaceAll()</td>
|
|
<td>Replaces each substring of this string that matches the given regular expression with the given replacement.</td>
|
|
</tr>
|
|
<tr>
|
|
<td>myString.compareTo()</td>
|
|
<td>Compares two strings lexicographically. The comparison is based on the Unicode value of each character in the strings.</td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<h3 id="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):</p>
|
|
<table>
|
|
<thead>
|
|
<tr>
|
|
<th>Methode</th>
|
|
<th>Beschreibung</th>
|
|
</tr>
|
|
</thead>
|
|
<tbody>
|
|
<tr>
|
|
<td>myNumber.compareTo()</td>
|
|
<td>Compares two Integer objects numerically.</td>
|
|
</tr>
|
|
<tr>
|
|
<td>myNumber.toString()</td>
|
|
<td>Returns a String object representing this Integer's value.</td>
|
|
</tr>
|
|
<tr>
|
|
<td>myNumber.intValue()</td>
|
|
<td>Returns the value of this Integer as an int.</td>
|
|
</tr>
|
|
<tr>
|
|
<td>myNumber.floatValue()</td>
|
|
<td>Returns the value of this Integer as a float after a widening primitive conversion.</td>
|
|
</tr>
|
|
<tr>
|
|
<td>myNumber.doubleValue()</td>
|
|
<td>Returns the value of this Integer as a double after a widening primitive conversion.</td>
|
|
</tr>
|
|
<tr>
|
|
<td>myNumber.shortValue()</td>
|
|
<td>Returns the value of this Integer as a short after a narrowing primitive conversion.</td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<h3 id="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:</p>
|
|
<table>
|
|
<thead>
|
|
<tr>
|
|
<th>Methode</th>
|
|
<th>Beschreibung</th>
|
|
</tr>
|
|
</thead>
|
|
<tbody>
|
|
<tr>
|
|
<td>Arrays.toString(Array a)</td>
|
|
<td>a string representation of the object.</td>
|
|
</tr>
|
|
<tr>
|
|
<td>Arrays.copyOf(Array a, int index)</td>
|
|
<td>Copies the specified array, truncating or padding with zeros (if necessary) so the copy has the specified length.</td>
|
|
</tr>
|
|
<tr>
|
|
<td>Arrays.compare(Array a, Array b)</td>
|
|
<td>Compares two int arrays lexicographically.</td>
|
|
</tr>
|
|
<tr>
|
|
<td>Arrays.equals(Array a, Array b)</td>
|
|
<td>Returns true if the two specified arrays of ints are equal to one another.</td>
|
|
</tr>
|
|
<tr>
|
|
<td>Arrays.sort(Array a)</td>
|
|
<td>Sorts the specified array into ascending numerical order</td>
|
|
</tr>
|
|
<tr>
|
|
<td>Arrays.fill(Array a, int number)</td>
|
|
<td>Assigns the specified int value to each element of the specified array of ints.</td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<h2 id="operatoren">Operatoren</h2>
|
|
<h3 id="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="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="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="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="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="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="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="schleifen">Schleifen</h2>
|
|
<h3 id="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="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="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="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="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="for-each-loop">for-each-loop</h3>
|
|
<h4 id="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="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="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="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>
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Letztes Update:
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<span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-datetime">November 4, 2022 16:13:00</span>
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<br>
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Erstellt:
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Authors: <span class='git-page-authors git-authors'><a href='mailto:yamidoesdev@gmail.com'>YamiDoesDev</a></span>
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