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    <div id="app"><!--[--><!--[--><!--[--><span tabindex="-1"></span><a href="#main-content" class="skip-link sr-only">Skip to content</a><!--]--><div class="theme-container has-toc"><!--[--><!--[--><header class="navbar"><div class="navbar-left"><button class="toggle-sidebar-button" title="Toggle Sidebar"><span class="icon"></span></button><!----><a href="/" class="brand"><img class="logo" src="http://cdn.tobebetterjavaer.com/tobebetterjavaer/images/logo-02.png" alt="Java 程序员进阶之路"><!----><span class="site-name hide-in-pad">Java 程序员进阶之路</span></a><!----></div><div class="navbar-center"><!----><nav class="nav-links"><div class="nav-item hide-in-mobile"><a href="/blog.html" class="nav-link" aria-label="博客"><span class="icon iconfont icon-gaishu" style=""></span>博客<!----></a></div><div class="nav-item hide-in-mobile"><a href="/home.html" class="nav-link" aria-label="进阶之路"><span class="icon iconfont icon-lujing" style=""></span>进阶之路<!----></a></div><div class="nav-item hide-in-mobile"><a 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class="button-bottom"></span></span></button></div></header><!----><!--]--><!----><div class="toggle-sidebar-wrapper"><span class="arrow left"></span></div><aside class="sidebar"><!--[--><!----><!--]--><ul class="sidebar-links"><li><!--[--><a href="/home.html" class="nav-link sidebar-link sidebar-page" aria-label="一、前言"><!---->一、前言<!----></a><ul class="sidebar-sub-headers"></ul><!--]--></li><li><!--[--><section class="sidebar-group"><button class="sidebar-heading clickable active"><!----><span class="title">二、Java核心</span><span class="arrow down"></span></button><ul class="sidebar-links"><li><!--[--><section class="sidebar-group"><button class="sidebar-heading clickable"><!----><span class="title">2.1 Java概述</span><span class="arrow right"></span></button><!----></section><!--]--></li><li><!--[--><section class="sidebar-group"><button class="sidebar-heading clickable"><!----><span class="title">2.2 Java语法基础</span><span class="arrow right"></span></button><!----></section><!--]--></li><li><!--[--><section class="sidebar-group"><button class="sidebar-heading clickable active"><!----><span class="title">2.3 数组&amp;字符串</span><span class="arrow down"></span></button><ul class="sidebar-links"><li><!--[--><a aria-current="page" href="/array/array.html" class="router-link-active router-link-exact-active nav-link active sidebar-link sidebar-page active" aria-label="Java数组"><!---->Java数组<!----></a><ul class="sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a href="/array/print.html" class="nav-link sidebar-link sidebar-page" aria-label="打印Java数组"><!---->打印Java数组<!----></a><ul class="sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a href="/string/immutable.html" class="nav-link sidebar-link sidebar-page" aria-label="为什么String是不可变的？"><!---->为什么String是不可变的？<!----></a><ul class="sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a href="/string/constant-pool.html" class="nav-link sidebar-link sidebar-page" aria-label="深入理解Java字符串常量池"><!---->深入理解Java字符串常量池<!----></a><ul class="sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a href="/string/intern.html" class="nav-link sidebar-link sidebar-page" aria-label="深入解析String.intern()方法"><!---->深入解析String.intern()方法<!----></a><ul class="sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a href="/string/equals.html" class="nav-link sidebar-link sidebar-page" aria-label="如何判断两个字符串是否相等？"><!---->如何判断两个字符串是否相等？<!----></a><ul class="sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a href="/string/join.html" class="nav-link sidebar-link sidebar-page" aria-label="Java字符串拼接"><!---->Java字符串拼接<!----></a><ul class="sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a href="/string/split.html" class="nav-link sidebar-link sidebar-page" aria-label="Java字符串分割"><!---->Java字符串分割<!----></a><ul class="sidebar-sub-headers"></ul><!--]--></li></ul></section><!--]--></li><li><!--[--><section class="sidebar-group"><button class="sidebar-heading clickable"><!----><span class="title">2.4 面向对象编程</span><span class="arrow right"></span></button><!----></section><!--]--></li><li><!--[--><section class="sidebar-group"><button class="sidebar-heading clickable"><!----><span class="title">2.5 集合框架（容器）</span><span class="arrow right"></span></button><!----></section><!--]--></li><li><!--[--><section class="sidebar-group"><button class="sidebar-heading clickable"><!----><span class="title">2.6 IO</span><span class="arrow right"></span></button><!----></section><!--]--></li><li><!--[--><section class="sidebar-group"><button class="sidebar-heading clickable"><!----><span class="title">2.7 异常处理</span><span class="arrow right"></span></button><!----></section><!--]--></li><li><!--[--><section class="sidebar-group"><button class="sidebar-heading clickable"><!----><span class="title">2.8 常用工具类</span><span class="arrow right"></span></button><!----></section><!--]--></li><li><!--[--><section class="sidebar-group"><button class="sidebar-heading clickable"><!----><span class="title">2.9 Java新特性</span><span class="arrow right"></span></button><!----></section><!--]--></li><li><!--[--><section class="sidebar-group"><button class="sidebar-heading clickable"><!----><span class="title">2.10 Java重要知识点</span><span class="arrow right"></span></button><!----></section><!--]--></li><li><!--[--><section class="sidebar-group"><button class="sidebar-heading clickable"><!----><span class="title">2.11 并发编程</span><span class="arrow right"></span></button><!----></section><!--]--></li><li><!--[--><section class="sidebar-group"><button class="sidebar-heading clickable"><!----><span class="title">2.12 JVM</span><span class="arrow right"></span></button><!----></section><!--]--></li></ul></section><!--]--></li><li><!--[--><section class="sidebar-group"><button class="sidebar-heading clickable"><!----><span class="title">三、Java企业级开发</span><span class="arrow right"></span></button><!----></section><!--]--></li><li><!--[--><section class="sidebar-group"><button class="sidebar-heading clickable"><!----><span class="title">四、数据库</span><span class="arrow right"></span></button><!----></section><!--]--></li><li><!--[--><section class="sidebar-group"><button class="sidebar-heading clickable"><!----><span class="title">五、计算机基础</span><span class="arrow right"></span></button><!----></section><!--]--></li><li><!--[--><section class="sidebar-group"><button class="sidebar-heading clickable"><!----><span class="title">六、求职面试</span><span class="arrow right"></span></button><!----></section><!--]--></li><li><!--[--><section class="sidebar-group"><button class="sidebar-heading clickable"><!----><span class="title">七、学习资源</span><span class="arrow right"></span></button><!----></section><!--]--></li><li><!--[--><section class="sidebar-group"><button class="sidebar-heading clickable"><!----><span class="title">八、学习建议</span><span class="arrow right"></span></button><!----></section><!--]--></li><li><!--[--><section class="sidebar-group"><button class="sidebar-heading clickable"><!----><span class="title">九、知识库搭建</span><span class="arrow right"></span></button><!----></section><!--]--></li><li><!--[--><section class="sidebar-group"><button class="sidebar-heading clickable"><!----><span class="title">十、联系作者</span><span class="arrow right"></span></button><!----></section><!--]--></li></ul><!--[--><!----><!--]--></aside><!--[--><main class="page" id="main-content"><!--[--><!----><nav class="breadcrumb disable"></nav><div class="page-title"><h1><!---->浅入浅出Java数组</h1><div class="page-info"><span class="author-info" aria-label="作者🖊" data-balloon-pos="down" isoriginal="false" pageview="false"><svg xmlns="http://www.w3.org/2000/svg" class="icon author-icon" viewbox="0 0 1024 1024" fill="currentColor" aria-label="author icon"><path d="M649.6 633.6c86.4-48 147.2-144 147.2-249.6 0-160-128-288-288-288s-288 128-288 288c0 108.8 57.6 201.6 147.2 249.6-121.6 48-214.4 153.6-240 288-3.2 9.6 0 19.2 6.4 25.6 3.2 9.6 12.8 12.8 22.4 12.8h704c9.6 0 19.2-3.2 25.6-12.8 6.4-6.4 9.6-16 6.4-25.6-25.6-134.4-121.6-240-243.2-288z"></path></svg><span><a class="author-item" href="/about-the-author/" target="_blank" rel="noopener noreferrer">沉默王二</a></span><span property="author" content="沉默王二"></span></span><!----><span class="date-info" aria-label="写作日期📅" data-balloon-pos="down" isoriginal="false" pageview="false"><svg xmlns="http://www.w3.org/2000/svg" class="icon calendar-icon" viewbox="0 0 1024 1024" fill="currentColor" aria-label="calendar icon"><path d="M716.4 110.137c0-18.753-14.72-33.473-33.472-33.473-18.753 0-33.473 14.72-33.473 33.473v33.473h66.993v-33.473zm-334.87 0c0-18.753-14.72-33.473-33.473-33.473s-33.52 14.72-33.52 33.473v33.473h66.993v-33.473zm468.81 33.52H716.4v100.465c0 18.753-14.72 33.473-33.472 33.473a33.145 33.145 0 01-33.473-33.473V143.657H381.53v100.465c0 18.753-14.72 33.473-33.473 33.473a33.145 33.145 0 01-33.473-33.473V143.657H180.6A134.314 134.314 0 0046.66 277.595v535.756A134.314 134.314 0 00180.6 947.289h669.74a134.36 134.36 0 00133.94-133.938V277.595a134.314 134.314 0 00-133.94-133.938zm33.473 267.877H147.126a33.145 33.145 0 01-33.473-33.473c0-18.752 14.72-33.473 33.473-33.473h736.687c18.752 0 33.472 14.72 33.472 33.473a33.145 33.145 0 01-33.472 33.473z"></path></svg><span>2021年10月22日</span><meta property="datePublished" content="2021-10-22T07:22:10.000Z"></span><span class="category-info" aria-label="分类🌈" data-balloon-pos="down" isoriginal="false" pageview="false"><svg xmlns="http://www.w3.org/2000/svg" class="icon category-icon" viewbox="0 0 1024 1024" fill="currentColor" aria-label="category icon"><path d="M148.41 106.992h282.176c22.263 0 40.31 18.048 40.31 40.31V429.48c0 22.263-18.047 40.31-40.31 40.31H148.41c-22.263 0-40.311-18.047-40.311-40.31V147.302c0-22.263 18.048-40.31 40.311-40.31zM147.556 553.478H429.73c22.263 0 40.311 18.048 40.311 40.31v282.176c0 22.263-18.048 40.312-40.31 40.312H147.555c-22.263 0-40.311-18.049-40.311-40.312V593.79c0-22.263 18.048-40.311 40.31-40.311zM593.927 106.992h282.176c22.263 0 40.31 18.048 40.31 40.31V429.48c0 22.263-18.047 40.31-40.31 40.31H593.927c-22.263 0-40.311-18.047-40.311-40.31V147.302c0-22.263 18.048-40.31 40.31-40.31zM730.22 920.502H623.926c-40.925 0-74.22-33.388-74.22-74.425V623.992c0-41.038 33.387-74.424 74.425-74.424h222.085c41.038 0 74.424 33.226 74.424 74.067v114.233c0 10.244-8.304 18.548-18.547 18.548s-18.548-8.304-18.548-18.548V623.635c0-20.388-16.746-36.974-37.33-36.974H624.13c-20.585 0-37.331 16.747-37.331 37.33v222.086c0 20.585 16.654 37.331 37.126 37.331H730.22c10.243 0 18.547 8.304 18.547 18.547 0 10.244-8.304 18.547-18.547 18.547z"></path></svg><ul class="categories-wrapper"><li class="category category0 clickable" role="navigation">Java核心</li><meta property="articleSection" content="Java核心"></ul></span><span aria-label="标签🏷" data-balloon-pos="down" isoriginal="false" pageview="false"><svg xmlns="http://www.w3.org/2000/svg" class="icon tag-icon" viewbox="0 0 1024 1024" fill="currentColor" aria-label="tag icon"><path d="M939.902 458.563L910.17 144.567c-1.507-16.272-14.465-29.13-30.737-30.737L565.438 84.098h-.402c-3.215 0-5.726 1.005-7.634 2.913l-470.39 470.39a10.004 10.004 0 000 14.164l365.423 365.424c1.909 1.908 4.42 2.913 7.132 2.913s5.223-1.005 7.132-2.913l470.39-470.39c2.01-2.11 3.014-5.023 2.813-8.036zm-240.067-72.121c-35.458 0-64.286-28.828-64.286-64.286s28.828-64.285 64.286-64.285 64.286 28.828 64.286 64.285-28.829 64.286-64.286 64.286z"></path></svg><ul class="tags-wrapper"><li class="tag tag5 clickable" role="navigation">数组&amp;字符串</li></ul><meta property="keywords" content="数组&amp;字符串"></span><span class="reading-time-info" aria-label="阅读时间⌛" data-balloon-pos="down" isoriginal="false" pageview="false"><svg xmlns="http://www.w3.org/2000/svg" class="icon timer-icon" viewbox="0 0 1024 1024" fill="currentColor" aria-label="timer icon"><path d="M799.387 122.15c4.402-2.978 7.38-7.897 7.38-13.463v-1.165c0-8.933-7.38-16.312-16.312-16.312H256.33c-8.933 0-16.311 7.38-16.311 16.312v1.165c0 5.825 2.977 10.874 7.637 13.592 4.143 194.44 97.22 354.963 220.201 392.763-122.204 37.542-214.893 196.511-220.2 389.397-4.661 5.049-7.638 11.651-7.638 19.03v5.825h566.49v-5.825c0-7.379-2.849-13.981-7.509-18.9-5.049-193.016-97.867-351.985-220.2-389.527 123.24-37.67 216.446-198.453 220.588-392.892zM531.16 450.445v352.632c117.674 1.553 211.787 40.778 211.787 88.676H304.097c0-48.286 95.149-87.382 213.728-88.676V450.445c-93.077-3.107-167.901-81.297-167.901-177.093 0-8.803 6.99-15.793 15.793-15.793 8.803 0 15.794 6.99 15.794 15.793 0 80.261 63.69 145.635 142.01 145.635s142.011-65.374 142.011-145.635c0-8.803 6.99-15.793 15.794-15.793s15.793 6.99 15.793 15.793c0 95.019-73.789 172.82-165.96 177.093z"></path></svg><span>大约 7 分钟</span><meta property="timeRequired" content="PT7M"></span></div><hr></div><!----><!----><div class="theme-hope-content"><p>“二哥，我看你公众号的一篇文章里提到，ArrayList 的内部是用数组实现的，我就对数组非常感兴趣，想深入地了解一下，今天终于到这个环节了，好期待呀！”三妹的语气里显得很兴奋。</p><p>“的确是的，看 ArrayList 的源码就一清二楚了。”我一边说，一边打开 Intellij IDEA，并找到了 ArrayList 的源码。</p><div class="language-java ext-java line-numbers-mode"><pre class="language-java"><code><span class="token doc-comment comment">/**
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 * The array buffer into which the elements of the ArrayList are stored.
 * The capacity of the ArrayList is the length of this array buffer. Any
 * empty ArrayList with elementData == DEFAULTCAPACITY_EMPTY_ELEMENTDATA
 * will be expanded to DEFAULT_CAPACITY when the first element is added.
 */</span>
<span class="token keyword">transient</span> <span class="token class-name">Object</span><span class="token punctuation">[</span><span class="token punctuation">]</span> elementData<span class="token punctuation">;</span> <span class="token comment">// non-private to simplify nested class access</span>

<span class="token doc-comment comment">/**
 * The size of the ArrayList (the number of elements it contains).
 *
 * <span class="token keyword">@serial</span>
 */</span>
<span class="token keyword">private</span> <span class="token keyword">int</span> size<span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>“瞧见没？<code>Object[] elementData</code> 就是数组。”我指着显示屏上这串代码继续说。</p><p>数组是一个对象，它包含了一组固定数量的元素，并且这些元素的类型是相同的。数组会按照索引的方式将元素放在指定的位置上，意味着我们可以通过索引来访问这些元素。在 Java 中，索引是从 0 开始的。</p><p>“哥，能说一下为什么索引从 0 开始吗？”三妹突然这个话题很感兴趣。</p><p>“哦，Java 是基于 C/C++ 语言实现的，而 C 语言的下标是从 0 开始的，所以 Java 就继承了这个良好的传统习惯。C语言有一个很重要概念，叫做指针，它实际上是一个偏移量，距离开始位置的偏移量，第一个元素就在开始的位置，它的偏移量就为 0，所以索引就为 0。”此刻，我很自信。</p><p>“此外，还有另外一种说法。早期的计算机资源比较匮乏，0 作为起始下标相比较于 1 作为起始下标，编译的效率更高。”</p><p>“哦。”三妹意味深长地点了点头。</p><p>我们可以将数组理解为一个个整齐排列的单元格，每个单元格里面存放着一个元素。</p><p>数组元素的类型可以是基本数据类型（比如说 int、double），也可以是引用数据类型（比如说 String），包括自定义类型。</p><p>数组的声明方式分两种。</p><p>先来看第一种：</p><div class="language-java ext-java line-numbers-mode"><pre class="language-java"><code><span class="token keyword">int</span><span class="token punctuation">[</span><span class="token punctuation">]</span> anArray<span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>再来看第二种：</p><div class="language-java ext-java line-numbers-mode"><pre class="language-java"><code><span class="token keyword">int</span> anOtherArray<span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>不同之处就在于中括号的位置，是跟在类型关键字的后面，还是跟在变量的名称的后面。前一种的使用频率更高一些，像 ArrayList 的源码中就用了第一种方式。</p><p>同样的，数组的初始化方式也有多种，最常见的是：</p><div class="language-java ext-java line-numbers-mode"><pre class="language-java"><code><span class="token keyword">int</span><span class="token punctuation">[</span><span class="token punctuation">]</span> anArray <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token keyword">int</span><span class="token punctuation">[</span><span class="token number">10</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
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62 
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>看到了没？上面这行代码中使用了 new 关键字，这就意味着数组的确是一个对象，只有对象的创建才会用到 new 关键字，<a href="https://tobebetterjavaer.com/basic-grammar/basic-data-type.html" target="_blank" rel="noopener noreferrer">基本数据类型<span><svg class="external-link-icon" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewbox="0 0 100 100" width="15" height="15"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path><polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg><span class="external-link-icon-sr-only">open in new window</span></span></a>是不用的。然后，我们需要在方括号中指定数组的长度。</p><p>这时候，数组中的每个元素都会被初始化为默认值，int 类型的就为 0，Object 类型的就为 null。 不同数据类型的默认值不同，可以参照<a href="https://tobebetterjavaer.com/basic-grammar/basic-data-type.html" target="_blank" rel="noopener noreferrer">之前的文章<span><svg class="external-link-icon" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewbox="0 0 100 100" width="15" height="15"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path><polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg><span class="external-link-icon-sr-only">open in new window</span></span></a>。</p><p>另外，还可以使用大括号的方式，直接初始化数组中的元素：</p><div class="language-java ext-java line-numbers-mode"><pre class="language-java"><code><span class="token keyword">int</span> anOtherArray<span class="token punctuation">[</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token keyword">int</span><span class="token punctuation">[</span><span class="token punctuation">]</span> <span class="token punctuation">{</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">,</span> <span class="token number">4</span><span class="token punctuation">,</span> <span class="token number">5</span><span class="token punctuation">}</span><span class="token punctuation">;</span>
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</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>这时候，数组的元素分别是 1、2、3、4、5，索引依次是 0、1、2、3、4，长度是 5。</p><p>“哥，怎么访问数组呢？”三妹及时地插话到。</p><p>前面提到过，可以通过索引来访问数组的元素，就像下面这样：</p><div class="language-java ext-java line-numbers-mode"><pre class="language-java"><code>anArray<span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token number">10</span><span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>变量名，加上中括号，加上元素的索引，就可以访问到数组，通过“=”操作符可以对元素进行赋值。</p><p>如果索引的值超出了数组的界限，就会抛出 <code>ArrayIndexOutOfBoundException</code>。</p><p>既然数组的索引是从 0 开始，那就是到数组的 <code>length - 1</code> 结束，不要使用超出这个范围内的索引访问数组，就不会抛出数组越界的异常了。</p><p>当数组的元素非常多的时候，逐个访问数组就太辛苦了，所以需要通过遍历的方式。</p><p>第一种，使用 for 循环：</p><div class="language-java ext-java line-numbers-mode"><pre class="language-java"><code><span class="token keyword">int</span> anOtherArray<span class="token punctuation">[</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token keyword">int</span><span class="token punctuation">[</span><span class="token punctuation">]</span> <span class="token punctuation">{</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">,</span> <span class="token number">4</span><span class="token punctuation">,</span> <span class="token number">5</span><span class="token punctuation">}</span><span class="token punctuation">;</span>
<span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token keyword">int</span> i <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> i <span class="token operator">&lt;</span> anOtherArray<span class="token punctuation">.</span>length<span class="token punctuation">;</span> i<span class="token operator">++</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>anOtherArray<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>通过 length 属性获取到数组的长度，然后从 0 开始遍历，就得到了数组的所有元素。</p><p>第二种，使用 for-each 循环：</p><div class="language-java ext-java line-numbers-mode"><pre class="language-java"><code><span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token keyword">int</span> element <span class="token operator">:</span> anOtherArray<span class="token punctuation">)</span> <span class="token punctuation">{</span>
    <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>element<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>如果不需要关心索引的话（意味着不需要修改数组的某个元素），使用 for-each 遍历更简洁一些。当然，也可以使用 while 和 do-while 循环。</p><p>在 Java 中，可变参数用于将任意数量的参数传递给方法，来看 <code>varargsMethod()</code> 方法：</p><div class="language-java ext-java line-numbers-mode"><pre class="language-java"><code><span class="token keyword">void</span> <span class="token function">varargsMethod</span><span class="token punctuation">(</span><span class="token class-name">String</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span> varargs<span class="token punctuation">)</span> <span class="token punctuation">{</span><span class="token punctuation">}</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>该方法可以接收任意数量的字符串参数，可以是 0 个或者 N 个，本质上，可变参数就是通过数组实现的。为了证明这一点，我们可以看一下反编译一后的字节码：</p><div class="language-java ext-java line-numbers-mode"><pre class="language-java"><code><span class="token keyword">public</span> <span class="token keyword">class</span> <span class="token class-name">VarargsDemo</span>
<span class="token punctuation">{</span>

    <span class="token keyword">public</span> <span class="token class-name">VarargsDemo</span><span class="token punctuation">(</span><span class="token punctuation">)</span>
    <span class="token punctuation">{</span>
    <span class="token punctuation">}</span>

    <span class="token keyword">transient</span> <span class="token keyword">void</span> <span class="token function">varargsMethod</span><span class="token punctuation">(</span><span class="token class-name">String</span> as<span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">)</span>
    <span class="token punctuation">{</span>
    <span class="token punctuation">}</span>
<span class="token punctuation">}</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>所以，我们其实可以直接将数组作为参数传递给该方法：</p><div class="language-java ext-java line-numbers-mode"><pre class="language-java"><code><span class="token class-name">VarargsDemo</span> demo <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">VarargsDemo</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token class-name">String</span><span class="token punctuation">[</span><span class="token punctuation">]</span> anArray <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">String</span><span class="token punctuation">[</span><span class="token punctuation">]</span> <span class="token punctuation">{</span><span class="token string">&quot;沉默王二&quot;</span><span class="token punctuation">,</span> <span class="token string">&quot;一枚有趣的程序员&quot;</span><span class="token punctuation">}</span><span class="token punctuation">;</span>
demo<span class="token punctuation">.</span><span class="token function">varargsMethod</span><span class="token punctuation">(</span>anArray<span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>也可以直接传递多个字符串，通过逗号隔开的方式：</p><div class="language-java ext-java line-numbers-mode"><pre class="language-java"><code>demo<span class="token punctuation">.</span><span class="token function">varargsMethod</span><span class="token punctuation">(</span><span class="token string">&quot;沉默王二&quot;</span><span class="token punctuation">,</span> <span class="token string">&quot;一枚有趣的程序员&quot;</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>在 Java 中，数组与 List 关系非常密切。List 封装了很多常用的方法，方便我们对集合进行一些操作，而如果直接操作数组的话，有很多不便，因为数组本身没有提供这些封装好的操作，所以有时候我们需要把数组转成 List。</p><p>“怎么转呢？”三妹问到。</p><p>最原始的方式，就是通过遍历数组的方式，一个个将数组添加到 List 中。</p><div class="language-java ext-java line-numbers-mode"><pre class="language-java"><code><span class="token keyword">int</span><span class="token punctuation">[</span><span class="token punctuation">]</span> anArray <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token keyword">int</span><span class="token punctuation">[</span><span class="token punctuation">]</span> <span class="token punctuation">{</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">,</span> <span class="token number">4</span><span class="token punctuation">,</span> <span class="token number">5</span><span class="token punctuation">}</span><span class="token punctuation">;</span>

<span class="token class-name">List</span><span class="token generics"><span class="token punctuation">&lt;</span><span class="token class-name">Integer</span><span class="token punctuation">&gt;</span></span> aList <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">ArrayList</span><span class="token generics"><span class="token punctuation">&lt;</span><span class="token punctuation">&gt;</span></span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token keyword">int</span> element <span class="token operator">:</span> anArray<span class="token punctuation">)</span> <span class="token punctuation">{</span>
    aList<span class="token punctuation">.</span><span class="token function">add</span><span class="token punctuation">(</span>element<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>更优雅的方式是通过 Arrays 类的 <code>asList()</code> 方法：</p><div class="language-java ext-java line-numbers-mode"><pre class="language-java"><code><span class="token class-name">List</span><span class="token generics"><span class="token punctuation">&lt;</span><span class="token class-name">Integer</span><span class="token punctuation">&gt;</span></span> aList <span class="token operator">=</span> <span class="token class-name">Arrays</span><span class="token punctuation">.</span><span class="token function">asList</span><span class="token punctuation">(</span>anArray<span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>但需要注意的是，该方法返回的 ArrayList 并不是 <code>java.util.ArrayList</code>，它其实是 Arrays 类的一个内部类：</p><div class="language-java ext-java line-numbers-mode"><pre class="language-java"><code><span class="token keyword">private</span> <span class="token keyword">static</span> <span class="token keyword">class</span> <span class="token class-name">ArrayList</span><span class="token generics"><span class="token punctuation">&lt;</span><span class="token class-name">E</span><span class="token punctuation">&gt;</span></span> <span class="token keyword">extends</span> <span class="token class-name">AbstractList</span><span class="token generics"><span class="token punctuation">&lt;</span><span class="token class-name">E</span><span class="token punctuation">&gt;</span></span>
        <span class="token keyword">implements</span> <span class="token class-name">RandomAccess</span><span class="token punctuation">,</span> <span class="token class-name"><span class="token namespace">java<span class="token punctuation">.</span>io<span class="token punctuation">.</span></span>Serializable</span><span class="token punctuation">{</span><span class="token punctuation">}</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div></div></div><p>如果需要添加元素或者删除元素的话，需要把它转成 <code>java.util.ArrayList</code>。</p><div class="language-java ext-java line-numbers-mode"><pre class="language-java"><code><span class="token keyword">new</span> <span class="token class-name">ArrayList</span><span class="token generics"><span class="token punctuation">&lt;</span><span class="token punctuation">&gt;</span></span><span class="token punctuation">(</span><span class="token class-name">Arrays</span><span class="token punctuation">.</span><span class="token function">asList</span><span class="token punctuation">(</span>anArray<span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>Java 8 新增了 Stream 流的概念，这就意味着我们也可以将数组转成 Stream 进行操作。</p><div class="language-java ext-java line-numbers-mode"><pre class="language-java"><code><span class="token class-name">String</span><span class="token punctuation">[</span><span class="token punctuation">]</span> anArray <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">String</span><span class="token punctuation">[</span><span class="token punctuation">]</span> <span class="token punctuation">{</span><span class="token string">&quot;沉默王二&quot;</span><span class="token punctuation">,</span> <span class="token string">&quot;一枚有趣的程序员&quot;</span><span class="token punctuation">,</span> <span class="token string">&quot;好好珍重他&quot;</span><span class="token punctuation">}</span><span class="token punctuation">;</span>
<span class="token class-name">Stream</span><span class="token generics"><span class="token punctuation">&lt;</span><span class="token class-name">String</span><span class="token punctuation">&gt;</span></span> aStream <span class="token operator">=</span> <span class="token class-name">Arrays</span><span class="token punctuation">.</span><span class="token function">stream</span><span class="token punctuation">(</span>anArray<span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div></div></div><p>如果想对数组进行排序的话，可以使用 Arrays 类提供的 <code>sort()</code> 方法。</p><ul><li>基本数据类型按照升序排列</li><li>实现了 Comparable 接口的对象按照 <code>compareTo()</code> 的排序</li></ul><p>来看第一个例子：</p><div class="language-java ext-java line-numbers-mode"><pre class="language-java"><code><span class="token keyword">int</span><span class="token punctuation">[</span><span class="token punctuation">]</span> anArray <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token keyword">int</span><span class="token punctuation">[</span><span class="token punctuation">]</span> <span class="token punctuation">{</span><span class="token number">5</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">4</span><span class="token punctuation">,</span> <span class="token number">8</span><span class="token punctuation">}</span><span class="token punctuation">;</span>
<span class="token class-name">Arrays</span><span class="token punctuation">.</span><span class="token function">sort</span><span class="token punctuation">(</span>anArray<span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div></div></div><p>排序后的结果如下所示：</p><div class="language-java ext-java line-numbers-mode"><pre class="language-java"><code><span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">4</span><span class="token punctuation">,</span> <span class="token number">5</span><span class="token punctuation">,</span> <span class="token number">8</span><span class="token punctuation">]</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>来看第二个例子：</p><div class="language-java ext-java line-numbers-mode"><pre class="language-java"><code><span class="token class-name">String</span><span class="token punctuation">[</span><span class="token punctuation">]</span> yetAnotherArray <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">String</span><span class="token punctuation">[</span><span class="token punctuation">]</span> <span class="token punctuation">{</span><span class="token string">&quot;A&quot;</span><span class="token punctuation">,</span> <span class="token string">&quot;E&quot;</span><span class="token punctuation">,</span> <span class="token string">&quot;Z&quot;</span><span class="token punctuation">,</span> <span class="token string">&quot;B&quot;</span><span class="token punctuation">,</span> <span class="token string">&quot;C&quot;</span><span class="token punctuation">}</span><span class="token punctuation">;</span>
<span class="token class-name">Arrays</span><span class="token punctuation">.</span><span class="token function">sort</span><span class="token punctuation">(</span>yetAnotherArray<span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">,</span>
                <span class="token class-name">Comparator</span><span class="token punctuation">.</span><span class="token function">comparing</span><span class="token punctuation">(</span><span class="token class-name">String</span><span class="token operator">::</span><span class="token function">toString</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">reversed</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>只对 1-3 位置上的元素进行反序，所以结果如下所示：</p><div class="language-text ext-text line-numbers-mode"><pre class="language-text"><code>[A, Z, E, B, C]
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>有时候，我们需要从数组中查找某个具体的元素，最直接的方式就是通过遍历的方式：</p><div class="language-java ext-java line-numbers-mode"><pre class="language-java"><code><span class="token keyword">int</span><span class="token punctuation">[</span><span class="token punctuation">]</span> anArray <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token keyword">int</span><span class="token punctuation">[</span><span class="token punctuation">]</span> <span class="token punctuation">{</span><span class="token number">5</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">4</span><span class="token punctuation">,</span> <span class="token number">8</span><span class="token punctuation">}</span><span class="token punctuation">;</span>
<span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token keyword">int</span> i <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> i <span class="token operator">&lt;</span> anArray<span class="token punctuation">.</span>length<span class="token punctuation">;</span> i<span class="token operator">++</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    <span class="token keyword">if</span> <span class="token punctuation">(</span>anArray<span class="token punctuation">[</span>i<span class="token punctuation">]</span> <span class="token operator">==</span> <span class="token number">4</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
        <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">&quot;找到了 &quot;</span> <span class="token operator">+</span> i<span class="token punctuation">)</span><span class="token punctuation">;</span>
        <span class="token keyword">break</span><span class="token punctuation">;</span>
    <span class="token punctuation">}</span>
<span class="token punctuation">}</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>上例中从数组中查询元素 4，找到后通过 break 关键字退出循环。</p><p>如果数组提前进行了排序，就可以使用二分查找法，这样效率就会更高一些。<code>Arrays.binarySearch()</code> 方法可供我们使用，它需要传递一个数组，和要查找的元素。</p><div class="language-java ext-java line-numbers-mode"><pre class="language-java"><code><span class="token keyword">int</span><span class="token punctuation">[</span><span class="token punctuation">]</span> anArray <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token keyword">int</span><span class="token punctuation">[</span><span class="token punctuation">]</span> <span class="token punctuation">{</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">,</span> <span class="token number">4</span><span class="token punctuation">,</span> <span class="token number">5</span><span class="token punctuation">}</span><span class="token punctuation">;</span>
<span class="token keyword">int</span> index <span class="token operator">=</span> <span class="token class-name">Arrays</span><span class="token punctuation">.</span><span class="token function">binarySearch</span><span class="token punctuation">(</span>anArray<span class="token punctuation">,</span> <span class="token number">4</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
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</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div></div></div><p>“除了一维数组，还有二维数组，三妹你可以去研究下，比如说用二维数组打印一下杨辉三角。”说完，我就去阳台上休息了，留三妹在那里学习，不能打扰她。</p><p><img src="http://cdn.tobebetterjavaer.com/tobebetterjavaer/images/xingbiaogongzhonghao.png" alt=""></p></div><!----><footer class="page-meta"><div class="meta-item edit-link"><a href="https://github.com/itwanger/toBeBetterJavaer/edit/master/docs/array/array.md" rel="noopener noreferrer" target="_blank" aria-label="在 GitHub 上编辑此页" class="nav-link label"><!--[--><svg xmlns="http://www.w3.org/2000/svg" class="icon edit-icon" viewbox="0 0 1024 1024" fill="currentColor" aria-label="edit icon"><path d="M430.818 653.65a60.46 60.46 0 0 1-50.96-93.281l71.69-114.012 7.773-10.365L816.038 80.138A60.46 60.46 0 0 1 859.225 62a60.46 60.46 0 0 1 43.186 18.138l43.186 43.186a60.46 60.46 0 0 1 0 86.373L588.879 565.55l-8.637 8.637-117.466 68.234a60.46 60.46 0 0 1-31.958 11.229z"></path><path d="M728.802 962H252.891A190.883 190.883 0 0 1 62.008 771.98V296.934a190.883 190.883 0 0 1 190.883-192.61h267.754a60.46 60.46 0 0 1 0 120.92H252.891a69.962 69.962 0 0 0-69.098 69.099V771.98a69.962 69.962 0 0 0 69.098 69.098h475.911A69.962 69.962 0 0 0 797.9 771.98V503.363a60.46 60.46 0 1 1 120.922 0V771.98A190.883 190.883 0 0 1 728.802 962z"></path></svg><!--]-->在 GitHub 上编辑此页<span><svg class="external-link-icon" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewbox="0 0 100 100" width="15" height="15"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path><polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg><span class="external-link-icon-sr-only">open in new window</span></span><!----></a></div><div class="meta-item update-time"><span class="label">上次编辑于: </span><span class="info">2022/7/28 下午1:05:53</span></div><div class="meta-item contributors"><span class="label">贡献者: </span><!--[--><!--[--><span class="contributor" title="email: www.qing_gee@163.com">itwanger</span>,<!--]--><!--[--><span class="contributor" title="email: www.qing_gee@163.com">沉默王二</span><!--]--><!--]--></div></footer><nav class="page-nav"><!----><a href="/array/print.html" class="nav-link next" aria-label="打印Java数组"><div class="hint">下一页<span class="arrow right"></span></div><div class="link">打印Java数组<!----></div></a></nav><div class="giscus-wrapper input-top" style="display:block;">Loading...</div><!----><!--]--></main><!--]--><footer class="footer-wrapper"><div class="footer"><a href="https://beian.miit.gov.cn/" target="_blank">豫ICP备2021038026号-1</a><img src="https://cdn.tobebetterjavaer.com/tobebetterjavaer/images/beian.png" height="15px" width="15px" /><a target="_blank" href="http://www.beian.gov.cn/portal/registerSystemInfo?recordcode=41030502000411"><span>豫公网安备 41030502000411号</span></a></div><div class="copyright">Copyright © 2022 沉默王二</div></footer><!--]--></div><!--]--><!----><!----><!--]--></div>
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