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<meta name="keywords" content="Java,instanceof,instanceof关键字"><meta property="og:url" content="https://javabetter.cn/basic-extra-meal/instanceof.html"><meta property="og:site_name" content="二哥的Java进阶之路"><meta property="og:title" content="掌握 Java instanceof关键字"><meta property="og:description" content="本文详细讲解了Java中的instanceof关键字，包括其作用、用法、使用场景以及注意事项。文章通过实例解析，帮助读者深入理解instanceof关键字在Java编程中的重要性，提高编程水平和技巧。"><meta property="og:type" content="article"><meta property="og:locale" content="zh-CN"><meta property="og:updated_time" content="2023-09-04T05:16:42.000Z"><meta property="article:author" content="沉默王二"><meta property="article:tag" content="Java重要知识点"><meta property="article:modified_time" content="2023-09-04T05:16:42.000Z"><script type="application/ld+json">{"@context":"https://schema.org","@type":"Article","headline":"掌握 Java instanceof关键字","image":[""],"dateModified":"2023-09-04T05:16:42.000Z","author":[{"@type":"Person","name":"沉默王二","url":"/about-the-author/"}]}</script><meta name="robots" content="all"><meta name="author" content="沉默王二"><meta http-equiv="Cache-Control" content="no-cache, no-store, must-revalidate"><meta http-equiv="Pragma" content="no-cache"><meta http-equiv="Expires" content="0"><meta name="apple-mobile-web-app-capable" content="yes"><script>
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class="vp-sidebar-heading clickable active" type="button"><!----><span class="vp-sidebar-title">二、Java基础</span><span class="vp-arrow down"></span></button><ul class="vp-sidebar-links"><li><section class="vp-sidebar-group"><button class="vp-sidebar-heading clickable" type="button"><!----><span class="vp-sidebar-title">2.1 Java概述及环境配置</span><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-heading clickable" type="button"><!----><span class="vp-sidebar-title">2.2 Java语法基础</span><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-heading clickable" type="button"><!----><span class="vp-sidebar-title">2.3 数组&字符串</span><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-heading clickable active" type="button"><!----><span class="vp-sidebar-title">2.4 面向对象编程</span><span class="vp-arrow down"></span></button><ul class="vp-sidebar-links"><li><!--[--><a class="vp-link nav-link vp-sidebar-link vp-sidebar-page" href="/oo/object-class.html"><!---->Java中的类和对象<!----></a><ul class="vp-sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a class="vp-link nav-link vp-sidebar-link vp-sidebar-page" href="/oo/package.html"><!---->Java中的包<!----></a><ul class="vp-sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a class="vp-link nav-link vp-sidebar-link vp-sidebar-page" href="/oo/var.html"><!---->Java中的变量<!----></a><ul class="vp-sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a class="vp-link nav-link vp-sidebar-link vp-sidebar-page" href="/oo/method.html"><!---->Java中的方法<!----></a><ul class="vp-sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a class="vp-link nav-link vp-sidebar-link vp-sidebar-page" href="/basic-extra-meal/varables.html"><!---->Java可变参数<!----></a><ul class="vp-sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a class="vp-link nav-link vp-sidebar-link vp-sidebar-page" href="/oo/native-method.html"><!---->Java native方法<!----></a><ul class="vp-sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a class="vp-link nav-link vp-sidebar-link vp-sidebar-page" href="/oo/construct.html"><!---->Java构造方法<!----></a><ul class="vp-sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a class="vp-link nav-link vp-sidebar-link vp-sidebar-page" href="/oo/access-control.html"><!---->Java访问权限修饰符<!----></a><ul class="vp-sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a class="vp-link nav-link vp-sidebar-link vp-sidebar-page" href="/oo/code-init.html"><!---->Java代码初始化块<!----></a><ul class="vp-sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a class="vp-link nav-link vp-sidebar-link vp-sidebar-page" href="/oo/abstract.html"><!---->Java抽象类<!----></a><ul class="vp-sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a class="vp-link nav-link vp-sidebar-link vp-sidebar-page" href="/oo/interface.html"><!---->Java接口<!----></a><ul class="vp-sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a class="vp-link nav-link vp-sidebar-link vp-sidebar-page" href="/oo/inner-class.html"><!---->Java内部类<!----></a><ul class="vp-sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a class="vp-link nav-link vp-sidebar-link vp-sidebar-page" href="/oo/encapsulation-inheritance-polymorphism.html"><!---->Java封装继承多态<!----></a><ul class="vp-sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a class="vp-link nav-link vp-sidebar-link vp-sidebar-page" href="/oo/this-super.html"><!---->Java this和super关键字<!----></a><ul class="vp-sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a class="vp-link nav-link vp-sidebar-link vp-sidebar-page" href="/oo/static.html"><!---->Java static关键字<!----></a><ul class="vp-sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a class="vp-link nav-link vp-sidebar-link vp-sidebar-page" href="/oo/final.html"><!---->Java final关键字<!----></a><ul class="vp-sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a class="vp-link nav-link active vp-sidebar-link vp-sidebar-page active" href="/basic-extra-meal/instanceof.html"><!---->Java instanceof关键字<!----></a><ul class="vp-sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a class="vp-link nav-link vp-sidebar-link vp-sidebar-page" href="/basic-extra-meal/immutable.html"><!---->Java不可变对象<!----></a><ul class="vp-sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a class="vp-link nav-link vp-sidebar-link vp-sidebar-page" href="/basic-extra-meal/override-overload.html"><!---->Java方法重写和方法重载<!----></a><ul class="vp-sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a class="vp-link nav-link vp-sidebar-link vp-sidebar-page" href="/basic-extra-meal/annotation.html"><!---->Java注解<!----></a><ul class="vp-sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a class="vp-link nav-link vp-sidebar-link vp-sidebar-page" href="/basic-extra-meal/enum.html"><!---->Java枚举（enum）<!----></a><ul class="vp-sidebar-sub-headers"></ul><!--]--></li></ul></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-heading clickable" type="button"><!----><span class="vp-sidebar-title">2.5 集合框架（容器）</span><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-heading clickable" type="button"><!----><span class="vp-sidebar-title">2.6 Java IO</span><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-heading clickable" type="button"><!----><span class="vp-sidebar-title">2.7 异常处理</span><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-heading clickable" type="button"><!----><span class="vp-sidebar-title">2.8 常用工具类</span><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-heading clickable" type="button"><!----><span class="vp-sidebar-title">2.9 Java新特性</span><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-heading clickable" type="button"><!----><span class="vp-sidebar-title">2.10 网络编程</span><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-heading clickable" type="button"><!----><span class="vp-sidebar-title">2.11 NIO</span><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-heading clickable" type="button"><!----><span class="vp-sidebar-title">2.12 Java重要知识点</span><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-heading clickable" type="button"><!----><span class="vp-sidebar-title">2.13 并发编程</span><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-heading clickable" type="button"><!----><span class="vp-sidebar-title">2.14 JVM</span><span class="vp-arrow end"></span></button><!----></section></li></ul></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-heading clickable" type="button"><!----><span class="vp-sidebar-title">三、Java进阶</span><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-heading clickable" type="button"><!----><span class="vp-sidebar-title">四、MySQL</span><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-heading clickable" type="button"><!----><span class="vp-sidebar-title">五、Redis</span><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-heading clickable" type="button"><!----><span class="vp-sidebar-title">六、计算机基础</span><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-heading clickable" type="button"><!----><span class="vp-sidebar-title">七、求职面试</span><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-heading clickable" type="button"><!----><span class="vp-sidebar-title">八、学习建议</span><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-heading clickable" type="button"><!----><span class="vp-sidebar-title">九、知识库搭建</span><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-heading clickable" type="button"><!----><span class="vp-sidebar-title">十、联系作者</span><span class="vp-arrow end"></span></button><!----></section></li></ul><!--[--><!----><!--]--></aside><!--[--><main id="main-content" class="vp-page"><!--[--><!----><!----><nav class="vp-breadcrumb disable"></nav><div class="vp-page-title"><h1><!---->掌握 Java instanceof关键字</h1><div class="page-info"><span class="page-author-info" aria-label="作者🖊" data-balloon-pos="down"><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="page-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="page-date-info" 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4 分钟</span><meta property="timeRequired" content="PT4M"></span></div><hr></div><!----><!----><div class="theme-hope-content"><h1 id="_5-17-java-instanceof关键字" tabindex="-1"><a class="header-anchor" href="#_5-17-java-instanceof关键字" aria-hidden="true">#</a> 5.17 Java instanceof关键字</h1><p>“三妹，今天我们来过一个非常简单的知识点，instanceof关键字。”</p><p>“用不着哥你来讲了，今天就换个形式，我来讲给你听。”三妹雄赳赳气昂昂地说。</p><p>instanceof 关键字的用法其实很简单：</p><div class="language-java line-numbers-mode" data-ext="java"><pre class="language-java"><code><span class="token punctuation">(</span>object<span class="token punctuation">)</span> <span class="token keyword">instanceof</span> <span class="token punctuation">(</span>type<span class="token punctuation">)</span>
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>用意也非常简单，判断对象是否符合指定的类型，结果要么是 true，要么是 false。在<a href="https://javabetter.cn/io/serialize.html" target="_blank" rel="noopener noreferrer">反序列化<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>的时候，instanceof 操作符还是蛮常用的，因为这时候我们不太确定对象属不属于指定的类型，如果不进行判断的话，就容易抛出 ClassCastException 异常。</p><p>我们来建这样一个简单的类 Round：</p><div class="language-java line-numbers-mode" data-ext="java"><pre class="language-java"><code><span class="token keyword">class</span> <span class="token class-name">Round</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>然后新增一个扩展类 Ring：</p><div class="language-java line-numbers-mode" data-ext="java"><pre class="language-java"><code><span class="token keyword">class</span> <span class="token class-name">Ring</span> <span class="token keyword">extends</span> <span class="token class-name">Round</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>这时候，我们就可以通过 instanceof 来检查 Ring 对象是否属于 Round 类型。</p><div class="language-java line-numbers-mode" data-ext="java"><pre class="language-java"><code><span class="token class-name">Ring</span> ring <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">Ring</span><span class="token punctuation">(</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>ring <span class="token keyword">instanceof</span> <span class="token class-name">Round</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>结果会输出 true，因为 Ring 继承了 Round，也就意味着 Ring 和 Round 符合 <code> is-a</code> 的关系，而 instanceof 操作符正是基于类与类之间的继承关系，以及类与接口之间的实现关系的。</p><p>我们再来新建一个接口 Shape：</p><div class="language-java line-numbers-mode" data-ext="java"><pre class="language-java"><code><span class="token keyword">interface</span> <span class="token class-name">Shape</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>然后新建 Circle 类实现 Shape 接口并继承 Round 类：</p><div class="language-java line-numbers-mode" data-ext="java"><pre class="language-java"><code><span class="token keyword">class</span> <span class="token class-name">Circle</span> <span class="token keyword">extends</span> <span class="token class-name">Round</span> <span class="token keyword">implements</span> <span class="token class-name">Shape</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>如果对象是由该类创建的，那么 instanceof 的结果肯定为 true。</p><div class="language-java line-numbers-mode" data-ext="java"><pre class="language-java"><code><span class="token class-name">Circle</span> circle <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">Circle</span><span class="token punctuation">(</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>circle <span class="token keyword">instanceof</span> <span class="token class-name">Circle</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>这个肯定没毛病，instanceof 就是干这个活的，大家也很好理解。那如果类型是父类呢？</p><div class="language-java line-numbers-mode" data-ext="java"><pre class="language-java"><code><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>circle <span class="token keyword">instanceof</span> <span class="token class-name">Round</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>结果肯定还是 true，因为依然符合 <code>is-a</code> 的关系。那如果类型为接口呢？</p><div class="language-java line-numbers-mode" data-ext="java"><pre class="language-java"><code><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>circle <span class="token keyword">instanceof</span> <span class="token class-name">Shape</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>结果仍然为 true， 因为也符合 <code>is-a</code> 的关系。如果要比较的对象和要比较的类型之间没有关系，当然是不能使用 instanceof 进行比较的。</p><p>为了验证这一点，我们来创建一个实现了 Shape 但与 Circle 无关的 Triangle 类：</p><div class="language-java line-numbers-mode" data-ext="java"><pre class="language-java"><code><span class="token keyword">class</span> <span class="token class-name">Triangle</span> <span class="token keyword">implements</span> <span class="token class-name">Shape</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>这时候，再使用 instanceof 进行比较的话，编译器就报错了。</p><div class="language-java line-numbers-mode" data-ext="java"><pre class="language-java"><code> <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>circle <span class="token keyword">instanceof</span> <span class="token class-name">Triangle</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>错误信息如下所示：</p><div class="language-text line-numbers-mode" data-ext="text"><pre class="language-text"><code>Inconvertible types; cannot cast 'com.itwanger.twentyfour.instanceof1.Circle' to 'com.itwanger.twentyfour.instanceof1.Triangle'
</code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>意思就是类型不匹配，不能转换，我们使用 instanceof 比较的目的，也就是希望如果结果为 true 的时候能进行类型转换。但显然 Circle 不能转为 Triangle。</p><p>编译器已经提前帮我们预知了，很聪明。</p><p>Java 是一门面向对象的编程语言，也就意味着除了基本数据类型，所有的类都会隐式继承 Object 类。所以下面的结果肯定也会输出 true。</p><div class="language-java line-numbers-mode" data-ext="java"><pre class="language-java"><code><span class="token class-name">Thread</span> thread <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">Thread</span><span class="token punctuation">(</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>thread <span class="token keyword">instanceof</span> <span class="token class-name">Object</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>“那如果对象为 null 呢？”我这时候插话了。</p><p>“这个还真的是一个好问题啊。”三妹忍不住对我竖了一个大拇指。</p><div class="language-java line-numbers-mode" data-ext="java"><pre class="language-java"><code><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 keyword">null</span> <span class="token keyword">instanceof</span> <span class="token class-name">Object</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>只有对象才会有 null 值，所以编译器是不会报错的，只不过，对于 null 来说，instanceof 的结果为 false。因为所有的对象都可以为 null，所以也不好确定 null 到底属于哪一个类。</p><p>通常，我们是这样使用 instanceof 操作符的。</p><div class="language-java line-numbers-mode" data-ext="java"><pre class="language-java"><code><span class="token comment">// 先判断类型</span>
<span class="token keyword">if</span> <span class="token punctuation">(</span>obj <span class="token keyword">instanceof</span> <span class="token class-name">String</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
<span class="token comment">// 然后强制转换</span>
<span class="token class-name">String</span> s <span class="token operator">=</span> <span class="token punctuation">(</span><span class="token class-name">String</span><span class="token punctuation">)</span> obj<span class="token punctuation">;</span>
<span class="token comment">// 然后才能使用</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>先用 instanceof 进行类型判断，然后再把 obj 强制转换成我们期望的类型再进行使用。</p><p>JDK 16 的时候，instanceof 模式匹配转了正，意味着使用 instanceof 的时候更便捷了。</p><div class="language-java line-numbers-mode" data-ext="java"><pre class="language-java"><code><span class="token keyword">if</span> <span class="token punctuation">(</span>obj <span class="token keyword">instanceof</span> <span class="token class-name">String</span> s<span class="token punctuation">)</span> <span class="token punctuation">{</span>
<span class="token comment">// 如果类型匹配 直接使用 s</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>可以直接在 if 条件判断类型的时候添加一个变量，就不需要再强转和声明新的变量了。</p><p>“哇，这样就简洁了呀！”为了配合三妹，我不仅惊叹到！</p><p>“好了，关于 instanceof 操作符我们就先讲到这吧，难是一点都不难，希望哥也能够很好的掌握。”三妹笑嘻嘻地说，看来她很享受这个讲的过程嘛。</p><hr><p>GitHub 上标星 9300+ 的开源知识库《<a href="https://github.com/itwanger/toBeBetterJavaer" target="_blank" rel="noopener noreferrer">二哥的 Java 进阶之路<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 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