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display: inline-block;">4</div>程序和计算机的那点事儿</p><!--]--></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-95d837d1 data-v-95d837d1><div class="item" data-v-95d837d1><div class="indicator" data-v-95d837d1></div><a class="VPLink link link" href="/courses/java/01-Java%E8%AF%AD%E6%B3%95%E5%85%A5%E9%97%A8/05-%E5%8F%98%E9%87%8F%E5%92%8C%E5%B8%B8%E9%87%8F" data-v-95d837d1><!--[--><p class="text" data-v-95d837d1><div class="text-color-gray mr-[6px]" style="font-weight: 550; display: inline-block;">5</div>变量和常量</p><!--]--></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-95d837d1 data-v-95d837d1><div class="item" data-v-95d837d1><div class="indicator" data-v-95d837d1></div><a class="VPLink link link" href="/courses/java/01-Java%E8%AF%AD%E6%B3%95%E5%85%A5%E9%97%A8/06-%E5%B8%B8%E7%94%A8%E7%9A%84%E8%BF%90%E7%AE%97%E7%AC%A6" data-v-95d837d1><!--[--><p class="text" data-v-95d837d1><div class="text-color-gray mr-[6px]" style="font-weight: 550; display: inline-block;">6</div>常用的运算符</p><!--]--></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-95d837d1 data-v-95d837d1><div class="item" data-v-95d837d1><div class="indicator" data-v-95d837d1></div><a class="VPLink link link" href="/courses/java/01-Java%E8%AF%AD%E6%B3%95%E5%85%A5%E9%97%A8/07-%E6%8E%A7%E5%88%B6%E8%AF%AD%E5%8F%A5%E5%92%8C%E6%B5%81%E7%A8%8B%E5%9B%BE" data-v-95d837d1><!--[--><p class="text" data-v-95d837d1><div class="text-color-gray mr-[6px]" style="font-weight: 550; display: inline-block;">7</div>控制语句和流程图</p><!--]--></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-95d837d1 data-v-95d837d1><div class="item" data-v-95d837d1><div class="indicator" data-v-95d837d1></div><a class="VPLink link link" href="/courses/java/01-Java%E8%AF%AD%E6%B3%95%E5%85%A5%E9%97%A8/08-if%E9%80%89%E6%8B%A9%E7%BB%93%E6%9E%84" data-v-95d837d1><!--[--><p class="text" data-v-95d837d1><div class="text-color-gray mr-[6px]" style="font-weight: 550; display: inline-block;">8</div>if选择结构</p><!--]--></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-95d837d1 data-v-95d837d1><div class="item" data-v-95d837d1><div class="indicator" data-v-95d837d1></div><a class="VPLink link link" href="/courses/java/01-Java%E8%AF%AD%E6%B3%95%E5%85%A5%E9%97%A8/09-switch%E9%80%89%E6%8B%A9%E7%BB%93%E6%9E%84" data-v-95d837d1><!--[--><p class="text" data-v-95d837d1><div class="text-color-gray mr-[6px]" style="font-weight: 550; display: inline-block;">9</div>switch选择结构</p><!--]--></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-95d837d1 data-v-95d837d1><div class="item" data-v-95d837d1><div class="indicator" data-v-95d837d1></div><a class="VPLink link link" href="/courses/java/01-Java%E8%AF%AD%E6%B3%95%E5%85%A5%E9%97%A8/10-%E5%BE%AA%E7%8E%AF%E7%BB%93%E6%9E%84" data-v-95d837d1><!--[--><p class="text" data-v-95d837d1><div class="text-color-gray mr-[6px]" style="font-weight: 550; display: inline-block;">10</div>循环结构</p><!--]--></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-95d837d1 data-v-95d837d1><div class="item" data-v-95d837d1><div class="indicator" data-v-95d837d1></div><a class="VPLink link link" href="/courses/java/01-Java%E8%AF%AD%E6%B3%95%E5%85%A5%E9%97%A8/11-%E5%A4%9A%E9%87%8D%E5%BE%AA%E7%8E%AF" data-v-95d837d1><!--[--><p class="text" data-v-95d837d1><div class="text-color-gray mr-[6px]" style="font-weight: 550; display: inline-block;">11</div>多重循环</p><!--]--></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-95d837d1 data-v-95d837d1><div class="item" data-v-95d837d1><div class="indicator" data-v-95d837d1></div><a class="VPLink link link" href="/courses/java/01-Java%E8%AF%AD%E6%B3%95%E5%85%A5%E9%97%A8/12-%E7%A8%8B%E5%BA%8F%E8%B0%83%E8%AF%95%E5%85%A5%E9%97%A8" data-v-95d837d1><!--[--><p class="text" data-v-95d837d1><div class="text-color-gray mr-[6px]" style="font-weight: 550; display: inline-block;">12</div>程序调试入门</p><!--]--></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-95d837d1 data-v-95d837d1><div class="item" data-v-95d837d1><div class="indicator" data-v-95d837d1></div><a class="VPLink link link" href="/courses/java/01-Java%E8%AF%AD%E6%B3%95%E5%85%A5%E9%97%A8/13-%E4%B8%80%E7%BB%B4%E6%95%B0%E7%BB%84" data-v-95d837d1><!--[--><p class="text" data-v-95d837d1><div class="text-color-gray mr-[6px]" style="font-weight: 550; display: inline-block;">13</div>一维数组</p><!--]--></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-95d837d1 data-v-95d837d1><div class="item" data-v-95d837d1><div class="indicator" data-v-95d837d1></div><a class="VPLink link link" href="/courses/java/01-Java%E8%AF%AD%E6%B3%95%E5%85%A5%E9%97%A8/14-%E5%A4%9A%E7%BB%B4%E6%95%B0%E7%BB%84" data-v-95d837d1><!--[--><p class="text" data-v-95d837d1><div class="text-color-gray mr-[6px]" style="font-weight: 550; display: inline-block;">14</div>多维数组</p><!--]--></a><!----></div><!----></div><!--]--></div></section></div><div class="group" data-v-802ad7d8><section class="VPSidebarItem level-0 collapsible collapsed" data-v-802ad7d8 data-v-95d837d1><div class="item" role="button" tabindex="0" data-v-95d837d1><div class="indicator" data-v-95d837d1></div><h2 class="text" data-v-95d837d1>Java面向对象 (1篇)</h2><div class="caret" role="button" aria-label="toggle section" tabindex="0" data-v-95d837d1><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" viewbox="0 0 24 24" class="caret-icon" data-v-95d837d1><path d="M9,19c-0.3,0-0.5-0.1-0.7-0.3c-0.4-0.4-0.4-1,0-1.4l5.3-5.3L8.3,6.7c-0.4-0.4-0.4-1,0-1.4s1-0.4,1.4,0l6,6c0.4,0.4,0.4,1,0,1.4l-6,6C9.5,18.9,9.3,19,9,19z"></path></svg></div></div><div class="items" data-v-95d837d1><!--[--><div class="VPSidebarItem level-1 is-link" data-v-95d837d1 data-v-95d837d1><div class="item" data-v-95d837d1><div class="indicator" data-v-95d837d1></div><a class="VPLink link link" href="/courses/java/02-Java%E9%9D%A2%E5%90%91%E5%AF%B9%E8%B1%A1/01-%E7%B1%BB%E5%92%8C%E5%AF%B9%E8%B1%A1" data-v-95d837d1><!--[--><p class="text" data-v-95d837d1><div class="text-color-red mr-[6px]" style="font-weight: 550; display: inline-block;">1</div>类和对象</p><!--]--></a><!----></div><!----></div><!--]--></div></section></div><div class="group" data-v-802ad7d8><section class="VPSidebarItem level-0 collapsible collapsed" data-v-802ad7d8 data-v-95d837d1><div class="item" role="button" tabindex="0" data-v-95d837d1><div class="indicator" data-v-95d837d1></div><h2 class="text" data-v-95d837d1>Java高级特性 (1篇)</h2><div class="caret" role="button" aria-label="toggle section" tabindex="0" data-v-95d837d1><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" viewbox="0 0 24 24" class="caret-icon" data-v-95d837d1><path d="M9,19c-0.3,0-0.5-0.1-0.7-0.3c-0.4-0.4-0.4-1,0-1.4l5.3-5.3L8.3,6.7c-0.4-0.4-0.4-1,0-1.4s1-0.4,1.4,0l6,6c0.4,0.4,0.4,1,0,1.4l-6,6C9.5,18.9,9.3,19,9,19z"></path></svg></div></div><div class="items" data-v-95d837d1><!--[--><div class="VPSidebarItem level-1 is-link" data-v-95d837d1 data-v-95d837d1><div class="item" data-v-95d837d1><div class="indicator" data-v-95d837d1></div><a class="VPLink link link" href="/courses/java/03-Java%E9%AB%98%E7%BA%A7%E7%89%B9%E6%80%A7/01-%E9%9B%86%E5%90%88%E4%B8%8E%E6%B3%9B%E5%9E%8B-1" data-v-95d837d1><!--[--><p class="text" data-v-95d837d1><div class="text-color-red mr-[6px]" style="font-weight: 550; display: inline-block;">1</div>集合与泛型-1</p><!--]--></a><!----></div><!----></div><!--]--></div></section></div><div class="group" data-v-802ad7d8><section class="VPSidebarItem level-0 collapsible collapsed" data-v-802ad7d8 data-v-95d837d1><div class="item" role="button" tabindex="0" data-v-95d837d1><div class="indicator" data-v-95d837d1></div><h2 class="text" data-v-95d837d1>附录 (1篇)</h2><div class="caret" role="button" aria-label="toggle section" tabindex="0" data-v-95d837d1><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" viewbox="0 0 24 24" class="caret-icon" data-v-95d837d1><path d="M9,19c-0.3,0-0.5-0.1-0.7-0.3c-0.4-0.4-0.4-1,0-1.4l5.3-5.3L8.3,6.7c-0.4-0.4-0.4-1,0-1.4s1-0.4,1.4,0l6,6c0.4,0.4,0.4,1,0,1.4l-6,6C9.5,18.9,9.3,19,9,19z"></path></svg></div></div><div class="items" data-v-95d837d1><!--[--><div class="VPSidebarItem level-1 is-link" data-v-95d837d1 data-v-95d837d1><div class="item" data-v-95d837d1><div class="indicator" data-v-95d837d1></div><a class="VPLink link link" href="/courses/java/04-%E9%99%84%E5%BD%95/01-CentOS%E5%AE%89%E8%A3%85JDK" data-v-95d837d1><!--[--><p class="text" data-v-95d837d1><div class="text-color-red mr-[6px]" style="font-weight: 550; display: inline-block;">1</div>CentOS 8.2 安装 JDK 1.8.0_202</p><!--]--></a><!----></div><!----></div><!--]--></div></section></div><!--]--><!--[--><!--]--></nav></aside><div class="VPContent has-sidebar" id="VPContent" data-v-03322d68 data-v-2c336b25><div class="VPDoc has-sidebar has-aside" data-v-2c336b25 data-v-53ed897c><!--[--><!--]--><div class="container" data-v-53ed897c><div class="aside" data-v-53ed897c><div class="aside-curtain" data-v-53ed897c></div><div class="aside-container" data-v-53ed897c><div class="aside-content" data-v-53ed897c><div class="VPDocAside" data-v-53ed897c data-v-3d450548><!--[--><!--]--><!--[--><!--]--><div class="VPDocAsideOutline" role="navigation" data-v-3d450548 data-v-70b38f01><div class="content" data-v-70b38f01><div class="outline-marker" data-v-70b38f01></div><div class="outline-title" role="heading" aria-level="2" data-v-70b38f01>目录</div><nav aria-labelledby="doc-outline-aria-label" data-v-70b38f01><span class="visually-hidden" id="doc-outline-aria-label" data-v-70b38f01> Table of Contents for current page </span><ul class="root" data-v-70b38f01 data-v-e10534d6><!--[--><!--]--></ul></nav></div></div><!--[--><!--]--><div class="spacer" data-v-3d450548></div><!--[--><!--]--><!----><!--[--><!--]--><!--[--><!--]--></div></div></div></div><div class="content" data-v-53ed897c><div class="content-container" data-v-53ed897c><!--[--><!--]--><!----><main class="main" data-v-53ed897c><div style="position:relative;" class="vp-doc _courses_java_01-Java%E8%AF%AD%E6%B3%95%E5%85%A5%E9%97%A8_08-if%E9%80%89%E6%8B%A9%E7%BB%93%E6%9E%84" data-v-53ed897c><div><h1 id="if选择结构" tabindex="-1">if选择结构 <a class="header-anchor" href="#if选择结构" aria-label="Permalink to "if选择结构""></a></h1><!----><h2 id="前言" tabindex="-1">前言 <a class="header-anchor" href="#前言" aria-label="Permalink to "前言""></a></h2><p><strong>C：</strong> 上一篇我们介绍了流程控制语句的概念，本篇我们要正式开始学习其中的选择控制语句。那么在 Java 中，如果要实现选择控制语句有哪些语法呢？</p><p>本篇我们就来看看其中，在以后用的最多的一种选择结构语法：if 系列选择结构。</p><p><img src="/assets/202010071229226.u6t1oD4Z.png" alt="202010071229226"></p><h2 id="基础if选择结构" tabindex="-1">基础if选择结构 <a class="header-anchor" href="#基础if选择结构" aria-label="Permalink to "基础if选择结构""></a></h2><p><strong>基础 if 选择结构</strong> 是 if 系列选择结构中，最基础的结构语法！它是最简单的选择结构，也只能用于一种流程分支的处理。</p><div class="language-java vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">java</span><pre class="shiki shiki-themes github-light github-dark-dimmed vp-code"><code><span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">// 语法</span></span>
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<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">// 条件往往是由关系运算符来组成的判断</span></span>
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<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">// 条件的结果是一个boolean值，要么为true(真)，要么为false(假)</span></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">if</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> (条件) {</span></span>
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<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> // 条件为真时执行的语句</span></span>
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<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">}</span></span></code></pre></div><!----><p><strong>案例需求：如果佩奇 Java 成绩大于 90 分，笔者将会奖励她一部 OnePlus 8 Pro。</strong></p><div class="language-java vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">java</span><pre class="shiki shiki-themes github-light github-dark-dimmed vp-code"><code><span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">// 声明一个变量用来存储佩奇的Java成绩</span></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">int</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> score</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> =</span><span style="--shiki-light:#005CC5;--shiki-dark:#6CB6FF;"> 91</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">;</span></span>
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<span class="line"></span>
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<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">// 套用基础if语法</span></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">if</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> (score </span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">></span><span style="--shiki-light:#005CC5;--shiki-dark:#6CB6FF;"> 90</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">) {</span></span>
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<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> System.out.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">println</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#96D0FF;">"笔者奖励了一部OnePlus 8 Pro。"</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">);</span></span>
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<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">}</span></span>
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<span class="line"></span>
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<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">System.out.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">println</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#96D0FF;">"程序结束！"</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">);</span></span></code></pre></div><div class="tip custom-block"><p class="custom-block-title">笔者说</p><p>套用下语法，用用关系运算符，就实现了一个很简单的选择案例，是不是很 easy。</p></div><h3 id="复杂条件的基础if" tabindex="-1">复杂条件的基础if <a class="header-anchor" href="#复杂条件的基础if" aria-label="Permalink to "复杂条件的基础if""></a></h3><p>接下来再看看下方案例中的条件，它就没有那么容易了。</p><p><strong>案例需求：如果乔治 Java 成绩大于 90 分，并且音乐成绩大于 80 分时，或者 Java 成绩等于 100 分，音乐成绩大于 70 分时，笔者会奖励他一部 OnePlus 8 Pro。</strong></p><p>面对这种场景，单靠普通的关系运算符显然无法实现，结合逻辑运算符就可以很好解决。</p><div class="language-java vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">java</span><pre class="shiki shiki-themes github-light github-dark-dimmed vp-code"><code><span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">// 声明变量分别存储乔治的Java成绩和音乐成绩</span></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">int</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> jScore</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> =</span><span style="--shiki-light:#005CC5;--shiki-dark:#6CB6FF;"> 60</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">;</span></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">int</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> mScore</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> =</span><span style="--shiki-light:#005CC5;--shiki-dark:#6CB6FF;"> 81</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">;</span></span>
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<span class="line"></span>
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<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">// 关系运算符结合逻辑运算符</span></span>
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<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">// 考虑到运算符的优先级，可以使用()来提升部分表达式的优先级，也是复杂条件下增加可读性的方法</span></span>
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<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">// ()的添加应该成为一种本能，它是义务教育阶段学数学后的条件反射</span></span>
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<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">if</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> ((jScore </span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">></span><span style="--shiki-light:#005CC5;--shiki-dark:#6CB6FF;"> 90</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> &&</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> mScore </span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">></span><span style="--shiki-light:#005CC5;--shiki-dark:#6CB6FF;"> 80</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">) </span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">||</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> (jScore </span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">==</span><span style="--shiki-light:#005CC5;--shiki-dark:#6CB6FF;"> 100</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> &&</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> mScore </span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">></span><span style="--shiki-light:#005CC5;--shiki-dark:#6CB6FF;"> 70</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">)) {</span></span>
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<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> System.out.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">println</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#96D0FF;">"笔者奖励了一部OnePlus 8 Pro。"</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">);</span></span>
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<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">}</span></span>
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<span class="line"></span>
|
||
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">System.out.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">println</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#96D0FF;">"程序结束！"</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">);</span></span></code></pre></div><h2 id="if-else选择结构" tabindex="-1">if-else选择结构 <a class="header-anchor" href="#if-else选择结构" aria-label="Permalink to "if-else选择结构""></a></h2><p>我们敲完上方的代码发现，如果条件不满足的话，好像什么处理情况也没有，这怎么可能，只有老师奖励学生，没有学生受罚？我们再来看个案例。</p><p><strong>案例需求：如果苏西 Java 考试成绩大于 90 分，笔者就奖励她一部 OnePlus 8 Pro，否则就罚她给笔者买一部 OnePlus 8 Pro。</strong></p><p>面对这个案例，我们还是可以采用基础If语法。</p><div class="language-java vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">java</span><pre class="shiki shiki-themes github-light github-dark-dimmed vp-code"><code><span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">// 条件成立情况</span></span>
|
||
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">if</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> (score </span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">></span><span style="--shiki-light:#005CC5;--shiki-dark:#6CB6FF;"> 90</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">) {</span></span>
|
||
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> System.out.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">println</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#96D0FF;">"笔者奖励了一部OnePlus 8 Pro。"</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">);</span></span>
|
||
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">}</span></span>
|
||
<span class="line"></span>
|
||
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">// 条件不成立情况</span></span>
|
||
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">// if (score <= 90) {</span></span>
|
||
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> // System.out.println("苏西哭着给笔者买了一部OnePlus 8 Pro，笔者很感动。");</span></span>
|
||
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">// }</span></span>
|
||
<span class="line"></span>
|
||
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">// 还可以这么写</span></span>
|
||
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">// !表示取反，也就是某种情况的相反情况</span></span>
|
||
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">if</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> (</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">!</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">(score </span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">></span><span style="--shiki-light:#005CC5;--shiki-dark:#6CB6FF;"> 90</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">)) {</span></span>
|
||
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> System.out.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">println</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#96D0FF;">"苏西哭着给笔者买了一部OnePlus 8 Pro，笔者很感动。"</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">);</span></span>
|
||
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">}</span></span></code></pre></div><p>但是明知道两个结果是互斥的，还要再写一次判断，并且条件越复杂，写起来就越麻烦。</p><p>例如：如果要基于刚才复杂条件的if案例来写的话。</p><div class="language-java vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">java</span><pre class="shiki shiki-themes github-light github-dark-dimmed vp-code"><code><span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">// 声明变量分别存储乔治的Java成绩和音乐成绩</span></span>
|
||
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">int</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> jScore</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> =</span><span style="--shiki-light:#005CC5;--shiki-dark:#6CB6FF;"> 60</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">;</span></span>
|
||
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">int</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> mScore</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> =</span><span style="--shiki-light:#005CC5;--shiki-dark:#6CB6FF;"> 81</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">;</span></span>
|
||
<span class="line"></span>
|
||
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">// 成立</span></span>
|
||
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">if</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> ((jScore </span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">></span><span style="--shiki-light:#005CC5;--shiki-dark:#6CB6FF;"> 90</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> &&</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> mScore </span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">></span><span style="--shiki-light:#005CC5;--shiki-dark:#6CB6FF;"> 80</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">) </span></span>
|
||
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> ||</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> (jScore </span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">==</span><span style="--shiki-light:#005CC5;--shiki-dark:#6CB6FF;"> 100</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> &&</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> mScore </span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">></span><span style="--shiki-light:#005CC5;--shiki-dark:#6CB6FF;"> 70</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">)) {</span></span>
|
||
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> System.out.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">println</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#96D0FF;">"笔者奖励了一部OnePlus 8 Pro。"</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">);</span></span>
|
||
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">}</span></span>
|
||
<span class="line"></span>
|
||
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">// 不成立的情况</span></span>
|
||
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">if</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> (</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">!</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">((jScore </span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">></span><span style="--shiki-light:#005CC5;--shiki-dark:#6CB6FF;"> 90</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> &&</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> mScore </span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">></span><span style="--shiki-light:#005CC5;--shiki-dark:#6CB6FF;"> 80</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">) </span></span>
|
||
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> ||</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> (jScore </span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">==</span><span style="--shiki-light:#005CC5;--shiki-dark:#6CB6FF;"> 100</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> &&</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> mScore </span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">></span><span style="--shiki-light:#005CC5;--shiki-dark:#6CB6FF;"> 70</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">))) {</span></span>
|
||
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> System.out.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">println</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#96D0FF;">"奖励乔治给笔者买了一部OnePlus 8 Pro。"</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">);</span></span>
|
||
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">}</span></span>
|
||
<span class="line"></span>
|
||
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">System.out.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">println</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#96D0FF;">"程序结束！"</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">);</span></span></code></pre></div><p><strong>头疼</strong> ，这时候我们可以使用 <code>if-else</code> 语法来轻松解决这种条件互斥的情况。<code>if-else</code> 选择结构可以处理简单的互斥分支情况。</p><div class="language-java vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">java</span><pre class="shiki shiki-themes github-light github-dark-dimmed vp-code"><code><span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">// 语法</span></span>
|
||
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">if</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> (条件) {</span></span>
|
||
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> // 语句1</span></span>
|
||
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">} </span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">else</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> {</span></span>
|
||
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> // 语句2</span></span>
|
||
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">}</span></span></code></pre></div><p><img src="/assets/202010071230720.tk45jvyd.png" alt="202010071230720"></p><!----><p>使用 <code>if-else</code> 来解决上述案例需求。</p><div class="language-java vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">java</span><pre class="shiki shiki-themes github-light github-dark-dimmed vp-code"><code><span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">// 声明一个变量存储苏西的Java考试成绩</span></span>
|
||
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">int</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> score</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> =</span><span style="--shiki-light:#005CC5;--shiki-dark:#6CB6FF;"> 90</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">;</span></span>
|
||
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">// 套用if-else语法</span></span>
|
||
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">// if：如果 else：否则</span></span>
|
||
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">if</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> (score </span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">></span><span style="--shiki-light:#005CC5;--shiki-dark:#6CB6FF;"> 90</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">) {</span></span>
|
||
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> System.out.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">println</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#96D0FF;">"笔者奖励了一部iPhone 11 Pro。"</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">);</span></span>
|
||
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">} </span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">else</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> {</span></span>
|
||
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> System.out.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">println</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#96D0FF;">"苏西哭着给笔者买了一部OnePlus 8 Pro，笔者很感动。"</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">);</span></span>
|
||
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">}</span></span></code></pre></div><div class="tip custom-block"><p class="custom-block-title">笔者说</p><p>实际上我们学的这些语法，在你念着案例时就能把代码写出来，如果（if）苏西的 Java 考试成绩（score）大于90分（> 90），笔者就奖励她一部 OnePlus 8 Pro（System.out.println("xxx");），否则（else）就罚她给笔者买一部 OnePlus 8 Pro（System.out.println("xxx");）。</p></div><h2 id="多重if选择结构" tabindex="-1">多重if选择结构 <a class="header-anchor" href="#多重if选择结构" aria-label="Permalink to "多重if选择结构""></a></h2><p>我们掌握了 <code>基础if</code> 来处理单分支选择，也掌握了 <code>if-else</code> 来处理互斥分支，但是如果出现了更多种的分支情况怎么办？</p><p><strong>案例需求：如果佩奇 Java 考试成绩大于等于 80 分，笔者就奖励她一部 OnePlus 8 Pro，如果佩奇 Java 考试成绩大于等于 60 分，笔者就奖励她一部一加云耳，否则就罚她给笔者买一部 iPhone 11 Pro。</strong></p><p>面对此需求，<code>if-else</code> 只能处理互斥分支所以不能采用，那使用 <code>基础if</code> 的方案如下。</p><div class="language-java vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">java</span><pre class="shiki shiki-themes github-light github-dark-dimmed vp-code"><code><span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">// 声明一个变量存储佩奇的Java考试成绩</span></span>
|
||
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">int</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> score</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> =</span><span style="--shiki-light:#005CC5;--shiki-dark:#6CB6FF;"> 90</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">;</span></span>
|
||
<span class="line"></span>
|
||
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">if</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> (score </span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">>=</span><span style="--shiki-light:#005CC5;--shiki-dark:#6CB6FF;"> 80</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">) {</span></span>
|
||
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> System.out.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">println</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#96D0FF;">"笔者奖励她一部OnePlus 8 Pro。"</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">);</span></span>
|
||
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">}</span></span>
|
||
<span class="line"></span>
|
||
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">// 如果不添加&&来进行限制，那么佩奇考试成绩>80分时，笔者将会破产</span></span>
|
||
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">if</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> (score </span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">>=</span><span style="--shiki-light:#005CC5;--shiki-dark:#6CB6FF;"> 60</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> &&</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> score </span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"><</span><span style="--shiki-light:#005CC5;--shiki-dark:#6CB6FF;"> 80</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">) {</span></span>
|
||
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> System.out.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">println</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#96D0FF;">"笔者奖励她一部一加云耳。"</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">);</span></span>
|
||
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">}</span></span>
|
||
<span class="line"></span>
|
||
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">if</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> (score </span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"><</span><span style="--shiki-light:#005CC5;--shiki-dark:#6CB6FF;"> 60</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">) {</span></span>
|
||
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> System.out.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">println</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#96D0FF;">"佩奇哭着给笔者买了一部iPhone 11 Pro，笔者很感动。"</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">);</span></span>
|
||
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">}</span></span></code></pre></div><p>毫无疑问，<code>基础if</code> 依然需要添加多次条件，但对于范围型判断来讲，如果不把范围控制好，那么后续的 if 条件就会出现多余判断的情况，因为每个 <code>基础if</code> 都是独立的，Java 为此提供了一种简化的方案：<code>多重if选择结构</code>。</p><p><strong>多重if选择结构：</strong> 可以处理分段的条件分支情况，<strong>它是自上而下进行选择判断，只要有一个条件满足，剩下的条件都不再执行判断</strong> 。所以不要随意排列条件，把容易满足的条件放在下方，不然容易满足的条件判断为 <code>true</code> 后，后续其他条件都不会再判断了。</p><div class="language-java vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">java</span><pre class="shiki shiki-themes github-light github-dark-dimmed vp-code"><code><span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">// 语法</span></span>
|
||
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">if</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> (条件1) {</span></span>
|
||
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> // 语句1</span></span>
|
||
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">} </span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">else</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> if</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">(条件2) { </span><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">// 可以有多个else if</span></span>
|
||
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> // 语句2</span></span>
|
||
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">} </span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">else</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> { </span><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">// 可以省略</span></span>
|
||
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> // 语句3</span></span>
|
||
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">}</span></span></code></pre></div><!----><div class="language-java vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">java</span><pre class="shiki shiki-themes github-light github-dark-dimmed vp-code"><code><span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">// 存储考试成绩</span></span>
|
||
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">int</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> score</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> =</span><span style="--shiki-light:#005CC5;--shiki-dark:#6CB6FF;"> 90</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">;</span></span>
|
||
<span class="line"></span>
|
||
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">// 套用if - else if - else语句</span></span>
|
||
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">/*</span></span>
|
||
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> * 注意事项：</span></span>
|
||
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> * 1.else if 必须配合if使用，if只能写一个，else if可以写很多个</span></span>
|
||
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> * 2.if-else if结构是自上而下进行判断选择的，只要上方的一个条件成立，下方的其他条件不再执行</span></span>
|
||
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> * 3.可以结合else来使用，当上方所有条件都不成立时，就会执行else语句内容</span></span>
|
||
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> */</span></span>
|
||
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">if</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> (score </span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">>=</span><span style="--shiki-light:#005CC5;--shiki-dark:#6CB6FF;"> 80</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">) {</span></span>
|
||
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> System.out.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">println</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#96D0FF;">"笔者奖励她一部OnePlus 8 Pro。"</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">);</span></span>
|
||
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">} </span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">else</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> if</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> (score </span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">>=</span><span style="--shiki-light:#005CC5;--shiki-dark:#6CB6FF;"> 60</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">) { </span><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">// 不需要限制 < 80的条件了，因为只要符合>=80，就不再向下判断</span></span>
|
||
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> System.out.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">println</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#96D0FF;">"笔者奖励她一部一加云耳。"</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">);</span></span>
|
||
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">} </span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">else</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> {</span></span>
|
||
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> System.out.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">println</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#96D0FF;">"佩奇哭着给笔者买了一部iPhone 11 Pro，笔者很感动。"</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">);</span></span>
|
||
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">}</span></span></code></pre></div><h2 id="嵌套if选择结构" tabindex="-1">嵌套if选择结构 <a class="header-anchor" href="#嵌套if选择结构" aria-label="Permalink to "嵌套if选择结构""></a></h2><p>生活在北上广深的各位同学们，对早晚高峰的地铁站印象很深了吧？在乘坐地铁前，我们需要有两次检查，第一次是安全检查，第二次是车票检查。火车站也是类似的。</p><p>面对这种多次检查，它的逻辑不是 <code>多重If</code> 这种自上而下依次执行的判断，而是当通过第一层判断后才可以进入第二层判断，面对这种场景，我们可以把 if 语句再灵活使用一点。</p><p><img src="/assets/202010071230999.F-m2rdiQ.png" alt="202010071230999"></p><p><strong>嵌套if</strong> 的应用场景：<strong>在之前条件满足的前提下，再增加额外的判断</strong> 。它可以通过外层语句和内层语句的协作，增强程序的灵活性。在笔者看来，当业务场景描述清楚的时候，福至心灵下就会自然而然的写出来对应的代码了。</p><div class="language-java vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">java</span><pre class="shiki shiki-themes github-light github-dark-dimmed vp-code"><code><span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">if</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> (条件1) {</span></span>
|
||
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> if</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> (条件2) </span></span>
|
||
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> // 语句1</span></span>
|
||
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> } </span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">else</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> {</span></span>
|
||
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> // 语句2</span></span>
|
||
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> }</span></span>
|
||
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">} </span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">else</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> {</span></span>
|
||
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> // 语句3</span></span>
|
||
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">}</span></span></code></pre></div><!----><p><strong>案例需求：学校举行运动会，百米赛跑跑入10秒内的学生有资格进决赛，然后根据性别进入男子组或女子组</strong></p><div class="language-java vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">java</span><pre class="shiki shiki-themes github-light github-dark-dimmed vp-code"><code><span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">// 声明一个变量存储百米成绩</span></span>
|
||
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">int</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> score</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> =</span><span style="--shiki-light:#005CC5;--shiki-dark:#6CB6FF;"> 9</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">;</span></span>
|
||
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">// 声明一个变量存储性别</span></span>
|
||
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">String</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> gender</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> =</span><span style="--shiki-light:#032F62;--shiki-dark:#96D0FF;"> "女"</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">;</span></span>
|
||
<span class="line"></span>
|
||
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">// 套用嵌套if语句</span></span>
|
||
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">// 注意事项：如果没有进入决赛，也就不会分配组别了</span></span>
|
||
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">if</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> (score </span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"><</span><span style="--shiki-light:#005CC5;--shiki-dark:#6CB6FF;"> 10</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">) { </span><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">// 可以进入决赛</span></span>
|
||
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> System.out.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">println</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#96D0FF;">"进入了决赛！"</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">);</span></span>
|
||
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> if</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> (</span><span style="--shiki-light:#032F62;--shiki-dark:#96D0FF;">"男"</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">equals</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">(gender)) { </span><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">// 分配组别</span></span>
|
||
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> System.out.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">println</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#96D0FF;">"进入了男子组！"</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">);</span></span>
|
||
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> } </span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">else</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> {</span></span>
|
||
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> System.out.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">println</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#96D0FF;">"进入了女子组！"</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">);</span></span>
|
||
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> }</span></span>
|
||
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">}</span></span></code></pre></div><h3 id="字符串的比较" tabindex="-1">字符串的比较 <a class="header-anchor" href="#字符串的比较" aria-label="Permalink to "字符串的比较""></a></h3><p>大多数情况下，我们比较内容时都会采用 <code>==</code> 这个关系运算符，但是如果遇到特殊类型，就不可以了。</p><p><strong>字符串的比较不要使用==，而是采用equals()方法。</strong></p><div class="tip custom-block"><p class="custom-block-title">笔者说</p><p>介绍数据类型时，笔者就说过 String 是个引用数据类型，有点特别。先了解，知道使用equals 方法来比较字符串内容即可。</p></div><div class="language-java vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">java</span><pre class="shiki shiki-themes github-light github-dark-dimmed vp-code"><code><span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">// == 号可以比较基本数据类型的值是否相等(八大基本数据类型)</span></span>
|
||
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">int</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> num1</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> =</span><span style="--shiki-light:#005CC5;--shiki-dark:#6CB6FF;"> 10</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">;</span></span>
|
||
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">int</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> num2</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> =</span><span style="--shiki-light:#005CC5;--shiki-dark:#6CB6FF;"> 10</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">;</span></span>
|
||
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">// System.out.println(num1 == num2); // true</span></span>
|
||
<span class="line"></span>
|
||
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">char</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> gender1</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> =</span><span style="--shiki-light:#032F62;--shiki-dark:#96D0FF;"> '男'</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">;</span></span>
|
||
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">char</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> gender2</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> =</span><span style="--shiki-light:#032F62;--shiki-dark:#96D0FF;"> '男'</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">;</span></span>
|
||
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">// System.out.println(gender1 == gender2); // true</span></span>
|
||
<span class="line"></span>
|
||
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">// ------------------</span></span>
|
||
<span class="line"></span>
|
||
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">// 如果是字符串，不要使用==号比较，而是使用equals()方法</span></span>
|
||
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">// 因为字符串是引用数据类型，==号如果比较引用数据类型，实际上比较的是数据的地址值而不是比较内容</span></span>
|
||
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">// 所以==很有可能导致你的字符串内容比较出问题，因为它比较的是地址值</span></span>
|
||
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">// 即使你发现两个字符串用==也比较为true了，那其实是涉及到常量池的概念了。</span></span>
|
||
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">// 先记住不要用==比较字符串就可以了！！！后期面向对象阶段学完就知道为啥了。</span></span>
|
||
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">String</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> str1</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> =</span><span style="--shiki-light:#032F62;--shiki-dark:#96D0FF;"> "我是一个字符串"</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">;</span></span>
|
||
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">String</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> str2</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> =</span><span style="--shiki-light:#032F62;--shiki-dark:#96D0FF;"> "我是一个字符串"</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">;</span></span>
|
||
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">System.out.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">println</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">(str1.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">equals</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">(str2));</span></span></code></pre></div><h2 id="答题环节" tabindex="-1">答题环节 <a class="header-anchor" href="#答题环节" aria-label="Permalink to "答题环节""></a></h2><p>光看不练假把式，来几个练习，练起来。</p><h3 id="模拟登录" tabindex="-1">模拟登录 <a class="header-anchor" href="#模拟登录" aria-label="Permalink to "模拟登录""></a></h3><details class="details custom-block"><summary>需求：使用 if 编写程序：从键盘获取用户名和密码，如果用户名和密码都正确，那么就显示"欢迎进入xxx的世界！"，否则就提示"用户名或密码错误！"。</summary><p>提示：可以预先设定一个假的用户名和密码。</p></details><p><img src="/assets/202010071232376.hFgK6mfi.png" alt="202010071232376"></p><h3 id="人机猜拳" tabindex="-1">人机猜拳 <a class="header-anchor" href="#人机猜拳" aria-label="Permalink to "人机猜拳""></a></h3><p>从控制台输入要出的拳，1代表石头、2代表剪刀、3代表布，电脑 <strong>随机</strong> 出拳，比较胜负，完成此代码功能。</p><p><img src="/assets/202010071232956.9Azuj1-R.png" alt="202010071232956"></p><h4 id="随机数的生成" tabindex="-1">随机数的生成 <a class="header-anchor" href="#随机数的生成" aria-label="Permalink to "随机数的生成""></a></h4><p>随机数是我们在程序中经常要使用到的，前期我们可以用它模拟很多业务，下面介绍一个 Java 中生成随机数的玩法。</p><div class="language-java vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">java</span><pre class="shiki shiki-themes github-light github-dark-dimmed vp-code"><code><span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">// Math.random()可以随机生成[0.0,1.0)之间的小数</span></span>
|
||
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">// [0.0,1.0)表示一个区间，等价于0.0 <= num1 < 1.0</span></span>
|
||
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">// 左闭右开就是包含左边数据，不包含右边的数据</span></span>
|
||
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">// [0.0,1.0]也表示一个区间，等价于0.0 <= num1 <= 1.0</span></span>
|
||
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">// 左闭右闭就是包含左边数据，也包含右边的数据</span></span>
|
||
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">// 想了解更多区间的内容，自己去百度下相关数学知识</span></span>
|
||
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">double</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> num1</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> =</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> Math.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">random</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">();</span></span>
|
||
<span class="line"></span>
|
||
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">/*</span></span>
|
||
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> * 基于上方的方法，如果想指定生成某个范围内的随机数，可以推导出一个公式。</span></span>
|
||
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> * 随机数公式为：(int)(Math.random() * (max - min)) + min;</span></span>
|
||
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> */</span></span>
|
||
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">// 案例1：生成[0,10)之间的随机整数</span></span>
|
||
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">// [0.0,1.0) * 10 --> [0,10)</span></span>
|
||
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">int</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> num2</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> =</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> (</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">int</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">)(Math.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">random</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">() </span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">*</span><span style="--shiki-light:#005CC5;--shiki-dark:#6CB6FF;"> 10</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">);</span></span>
|
||
<span class="line"></span>
|
||
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">// 案例2：生成[5,14)之间的随机整数</span></span>
|
||
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">int</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> num3</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> =</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> (</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">int</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">)(Math.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">random</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">() </span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">*</span><span style="--shiki-light:#005CC5;--shiki-dark:#6CB6FF;"> 9</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">) </span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">+</span><span style="--shiki-light:#005CC5;--shiki-dark:#6CB6FF;"> 5</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">;</span></span>
|
||
<span class="line"></span>
|
||
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">// 案例3：如果想生成[6,20]之间的随机整数，那可以将其理解为[6,21)，这样就可以再套上方的公式了</span></span>
|
||
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">int</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> num4</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> =</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> (</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">int</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">)(Math.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">random</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">() </span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">*</span><span style="--shiki-light:#005CC5;--shiki-dark:#6CB6FF;"> 15</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">) </span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">+</span><span style="--shiki-light:#005CC5;--shiki-dark:#6CB6FF;"> 6</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">;</span></span></code></pre></div><h3 id="幸运抽奖" tabindex="-1">幸运抽奖 <a class="header-anchor" href="#幸运抽奖" aria-label="Permalink to "幸运抽奖""></a></h3><details class="details custom-block"><summary>需求：实现幸运抽奖功能：输入4位的会员号，如果会员号的百位数字等于产生的随机数字，那么这个会员就是幸运会员，将奖励一部 iPhone 11 Pro！进行合理结果提示。</summary><p>提示：获取4位数，各个位的数字举例：</p></details><div class="language-java vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">java</span><pre class="shiki shiki-themes github-light github-dark-dimmed vp-code"><code><span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">int</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> num</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> =</span><span style="--shiki-light:#005CC5;--shiki-dark:#6CB6FF;"> 1234</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">;</span></span>
|
||
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">// 千位</span></span>
|
||
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">int</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> qian</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> =</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> num </span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">/</span><span style="--shiki-light:#005CC5;--shiki-dark:#6CB6FF;"> 1000</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">;</span></span>
|
||
<span class="line"></span>
|
||
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">// 百位</span></span>
|
||
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">int</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> bai</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> =</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> num </span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">/</span><span style="--shiki-light:#005CC5;--shiki-dark:#6CB6FF;"> 100</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> %</span><span style="--shiki-light:#005CC5;--shiki-dark:#6CB6FF;"> 10</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">;</span></span>
|
||
<span class="line"></span>
|
||
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">// 十位</span></span>
|
||
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">int</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> shi</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> =</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> num </span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">/</span><span style="--shiki-light:#005CC5;--shiki-dark:#6CB6FF;"> 10</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> %</span><span style="--shiki-light:#005CC5;--shiki-dark:#6CB6FF;"> 10</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">;</span></span>
|
||
<span class="line"></span>
|
||
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">// 个位</span></span>
|
||
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">int</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> ge</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> =</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> num </span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">%</span><span style="--shiki-light:#005CC5;--shiki-dark:#6CB6FF;"> 10</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> %</span><span style="--shiki-light:#005CC5;--shiki-dark:#6CB6FF;"> 10</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">;</span></span></code></pre></div><h2 id="后记" tabindex="-1">后记 <a class="header-anchor" href="#后记" aria-label="Permalink to "后记""></a></h2><p>选择结构的使用，一般不会困扰到大家。因为它与我们日常生活是非常贴近的，可读性非常强。当然如果还是不能理解，别忘了流程图哈！</p><div class="info custom-block"><p class="custom-block-title">笔者说</p><p>对于技术的学习，笔者一贯遵循的步骤是：先用最最简单的 demo 让它跑起来，然后学学它的最最常用 API 和 配置让自己能用起来，最后熟练使用的基础上，在空闲时尝试阅读它的源码让自己能够洞彻它的运行机制，部分问题出现的原因，同时借鉴这些技术实现来提升自己的代码高度。</p><p>所以在笔者的文章中，前期基本都是小白文，仅仅穿插很少量的源码研究。当然等小白文更新多了，你们还依然喜欢，后期会不定时专门对部分技术的源码进行解析。</p></div></div></div></main><footer class="VPDocFooter" data-v-53ed897c data-v-f3af8004><!--[--><!--[--><!--[--><!--[--><!----><!--]--><!--]--><!--]--><!--]--><div class="edit-info" data-v-f3af8004><div class="edit-link" data-v-f3af8004><a class="VPLink link vp-external-link-icon no-icon edit-link-button" href="https://github.com/Charles7c/charles7c.github.io/edit/main/docs/courses/java/01-Java语法入门/08-if选择结构.md" target="_blank" rel="noreferrer" data-v-f3af8004><!--[--><svg xmlns="http://www.w3.org/2000/svg" viewbox="0 0 24 24" class="edit-link-icon" aria-label="edit icon" data-v-f3af8004><path d="M18,23H4c-1.7,0-3-1.3-3-3V6c0-1.7,1.3-3,3-3h7c0.6,0,1,0.4,1,1s-0.4,1-1,1H4C3.4,5,3,5.4,3,6v14c0,0.6,0.4,1,1,1h14c0.6,0,1-0.4,1-1v-7c0-0.6,0.4-1,1-1s1,0.4,1,1v7C21,21.7,19.7,23,18,23z"></path><path d="M8,17c-0.3,0-0.5-0.1-0.7-0.3C7,16.5,6.9,16.1,7,15.8l1-4c0-0.2,0.1-0.3,0.3-0.5l9.5-9.5c1.2-1.2,3.2-1.2,4.4,0c1.2,1.2,1.2,3.2,0,4.4l-9.5,9.5c-0.1,0.1-0.3,0.2-0.5,0.3l-4,1C8.2,17,8.1,17,8,17zM9.9,12.5l-0.5,2.1l2.1-0.5l9.3-9.3c0.4-0.4,0.4-1.1,0-1.6c-0.4-0.4-1.2-0.4-1.6,0l0,0L9.9,12.5z M18.5,2.5L18.5,2.5L18.5,2.5z"></path></svg> 不妥之处，敬请雅正<!--]--></a></div><div class="last-updated" data-v-f3af8004><p class="VPLastUpdated" data-v-f3af8004 data-v-a25eb6f3>最后更新: <time datetime="2022-09-24T06:08:24.000Z" data-v-a25eb6f3></time></p></div></div><nav class="prev-next" data-v-f3af8004><div class="pager" data-v-f3af8004><a class="VPLink link pager-link prev" href="/courses/java/01-Java%E8%AF%AD%E6%B3%95%E5%85%A5%E9%97%A8/07-%E6%8E%A7%E5%88%B6%E8%AF%AD%E5%8F%A5%E5%92%8C%E6%B5%81%E7%A8%8B%E5%9B%BE" data-v-f3af8004><!--[--><span class="desc" data-v-f3af8004>上一篇</span><span class="title" data-v-f3af8004><div class="text-color-gray mr-[6px]" style="font-weight: 550; display: inline-block;">7</div>控制语句和流程图</span><!--]--></a></div><div class="pager" data-v-f3af8004><a class="VPLink link pager-link next" href="/courses/java/01-Java%E8%AF%AD%E6%B3%95%E5%85%A5%E9%97%A8/09-switch%E9%80%89%E6%8B%A9%E7%BB%93%E6%9E%84" data-v-f3af8004><!--[--><span class="desc" data-v-f3af8004>下一篇</span><span class="title" data-v-f3af8004><div class="text-color-gray mr-[6px]" style="font-weight: 550; display: inline-block;">9</div>switch选择结构</span><!--]--></a></div></nav></footer><!--[--><!--[--><!--[--><div id="comment-container"></div><!--]--><!--]--><!--]--></div></div></div><!--[--><!--]--></div></div><!----><!--[--><!--]--></div></div>
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display: inline-block;\\\">1</div>个人常用快捷键\",\"link\":\"/categories/fragments/2022/10/06/个人常用快捷键\"},{\"text\":\"<div class=\\\"text-color-orange mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">2</div>个人常用 Git 命令\",\"link\":\"/categories/fragments/2022/10/05/个人常用Git命令\"},{\"text\":\"<div class=\\\"text-color-yellow mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">3</div>个人常用 Docker 命令\",\"link\":\"/categories/fragments/2022/10/01/个人常用Docker命令\"},{\"text\":\"<div class=\\\"text-color-gray mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">4</div>个人常用 SQL 函数\",\"link\":\"/categories/fragments/2022/02/16/个人常用SQL函数\"},{\"text\":\"<div class=\\\"text-color-gray mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">5</div>个人常用 Linux 命令\",\"link\":\"/categories/fragments/2019/12/31/个人常用Linux命令\"},{\"text\":\"<div class=\\\"text-color-gray mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">6</div>个人常用 Hutool 工具类\",\"link\":\"/categories/fragments/2019/12/30/个人常用Hutool工具类\"},{\"text\":\"<div class=\\\"text-color-gray mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">7</div>个人常用 Stream 使用技巧\",\"link\":\"/categories/fragments/2019/12/29/个人常用Stream使用技巧\"},{\"text\":\"<div class=\\\"text-color-gray mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">8</div>个人 SQL 优化技巧\",\"link\":\"/categories/fragments/2019/12/28/个人SQL优化技巧\"}],\"collapsed\":false},{\"text\":\"<img class=\\\"chinese-zodiac\\\" style=\\\"position: static; vertical-align: middle; padding-bottom: 3px;\\\" src=\\\"/img/svg/chinese-zodiac/rabbit.svg\\\" title=\\\"兔年\\\" alt=\\\"生肖\\\">\\n 2023年 (1篇)\",\"items\":[{\"text\":\"<div class=\\\"text-color-red mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">1</div>阿里巴巴的Code Review方法论与实践总结\",\"link\":\"/categories/fragments/2023/01/06/CodeReview方法论与实践总结\"}],\"collapsed\":false},{\"text\":\"<img class=\\\"chinese-zodiac\\\" style=\\\"position: static; vertical-align: middle; padding-bottom: 3px;\\\" src=\\\"/img/svg/chinese-zodiac/tiger.svg\\\" title=\\\"虎年\\\" alt=\\\"生肖\\\">\\n 2022年 (15篇)\",\"items\":[{\"text\":\"<div class=\\\"text-color-red mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">1</div>简单聊聊如何让网站开启灰色显示\",\"link\":\"/categories/fragments/2022/12/07/网站开启灰色显示\"},{\"text\":\"<div class=\\\"text-color-orange mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">2</div>使用 IntelliJ IDEA 进行远程程序调试\",\"link\":\"/categories/fragments/2022/11/01/使用IDEA进行远程程序调试\"},{\"text\":\"<div class=\\\"text-color-yellow mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">3</div>CentOS 安装 Docker、Docker Compose\",\"link\":\"/categories/fragments/2022/10/31/CentOS安装Docker\"},{\"text\":\"<div class=\\\"text-color-gray mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">4</div>Docker 安装 MinIO 详细步骤\",\"link\":\"/categories/fragments/2022/10/28/Docker安装MinIO\"},{\"text\":\"<div class=\\\"text-color-gray mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">5</div>Docker 安装 Consul 详细步骤\",\"link\":\"/categories/fragments/2022/10/27/Docker安装Consul\"},{\"text\":\"<div class=\\\"text-color-gray mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">6</div>Docker 安装 OpenLDAP 详细步骤\",\"link\":\"/categories/fragments/2022/10/26/Docker安装OpenLDAP\"},{\"text\":\"<div class=\\\"text-color-gray mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">7</div>个人常用快捷键\",\"link\":\"/categories/fragments/2022/10/06/个人常用快捷键\"},{\"text\":\"<div class=\\\"text-color-gray mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">8</div>个人常用 Git 命令\",\"link\":\"/categories/fragments/2022/10/05/个人常用Git命令\"},{\"text\":\"<div class=\\\"text-color-gray mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">9</div>个人常用 Docker 命令\",\"link\":\"/categories/fragments/2022/10/01/个人常用Docker命令\"},{\"text\":\"<div class=\\\"text-color-gray mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">10</div>内网CentOS服务器设置网络代理\",\"link\":\"/categories/fragments/2022/08/29/内网CentOS服务器设置网络代理\"},{\"text\":\"<div class=\\\"text-color-gray mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">11</div>为指定Git仓库单独配置用户名和邮箱\",\"link\":\"/categories/fragments/2022/03/28/为指定Git仓库单独配置用户名和邮箱\"},{\"text\":\"<div class=\\\"text-color-gray mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">12</div>修改Git所有提交记录中的作者和邮箱\",\"link\":\"/categories/fragments/2022/03/27/修改Git所有提交记录中的作者和邮箱\"},{\"text\":\"<div class=\\\"text-color-gray mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">13</div>修改Git最后一次提交记录的作者和邮箱\",\"link\":\"/categories/fragments/2022/03/26/修改Git最后一次提交记录的作者和邮箱\"},{\"text\":\"<div class=\\\"text-color-gray mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">14</div>合并两个Git仓库的历史提交记录\",\"link\":\"/categories/fragments/2022/03/25/合并两个Git仓库的历史提交记录\"},{\"text\":\"<div class=\\\"text-color-gray mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">15</div>个人常用 SQL 函数\",\"link\":\"/categories/fragments/2022/02/16/个人常用SQL函数\"}],\"collapsed\":true},{\"text\":\"<img class=\\\"chinese-zodiac\\\" style=\\\"position: static; vertical-align: middle; padding-bottom: 3px;\\\" src=\\\"/img/svg/chinese-zodiac/ox.svg\\\" title=\\\"牛年\\\" alt=\\\"生肖\\\">\\n 2021年 (2篇)\",\"items\":[{\"text\":\"<div class=\\\"text-color-red mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">1</div>设计模式之单例模式\",\"link\":\"/categories/fragments/2021/05/29/设计模式之单例模式\"},{\"text\":\"<div class=\\\"text-color-orange mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">2</div>精密计算工具类-BigDecimal\",\"link\":\"/categories/fragments/2021/03/12/精密计算工具类-BigDecimal\"}],\"collapsed\":true},{\"text\":\"<img class=\\\"chinese-zodiac\\\" style=\\\"position: static; vertical-align: middle; padding-bottom: 3px;\\\" src=\\\"/img/svg/chinese-zodiac/pig.svg\\\" title=\\\"猪年\\\" alt=\\\"生肖\\\">\\n 2019年 (4篇)\",\"items\":[{\"text\":\"<div class=\\\"text-color-red mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">1</div>个人常用 Linux 命令\",\"link\":\"/categories/fragments/2019/12/31/个人常用Linux命令\"},{\"text\":\"<div class=\\\"text-color-orange mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">2</div>个人常用 Hutool 工具类\",\"link\":\"/categories/fragments/2019/12/30/个人常用Hutool工具类\"},{\"text\":\"<div class=\\\"text-color-yellow mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">3</div>个人常用 Stream 使用技巧\",\"link\":\"/categories/fragments/2019/12/29/个人常用Stream使用技巧\"},{\"text\":\"<div class=\\\"text-color-gray mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">4</div>个人 SQL 优化技巧\",\"link\":\"/categories/fragments/2019/12/28/个人SQL优化技巧\"}],\"collapsed\":true}],\"/categories/solutions/\":[{\"text\":\"<img class=\\\"chinese-zodiac\\\" style=\\\"position: static; vertical-align: middle; padding-bottom: 3px;\\\" src=\\\"/img/svg/chinese-zodiac/tiger.svg\\\" title=\\\"虎年\\\" alt=\\\"生肖\\\">\\n 2022年 (1篇)\",\"items\":[{\"text\":\"<div class=\\\"text-color-red mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">1</div>递归查询树型结构数据的性能优化方案\",\"link\":\"/categories/solutions/2022/09/07/递归查询树型结构数据的性能优化方案\"}],\"collapsed\":false},{\"text\":\"<img class=\\\"chinese-zodiac\\\" style=\\\"position: static; vertical-align: middle; padding-bottom: 3px;\\\" src=\\\"/img/svg/chinese-zodiac/ox.svg\\\" title=\\\"牛年\\\" alt=\\\"生肖\\\">\\n 2021年 (2篇)\",\"items\":[{\"text\":\"<div class=\\\"text-color-red mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">1</div>一条SQL查询今年每月统计信息\",\"link\":\"/categories/solutions/2021/11/22/一条SQL查询今年每月统计信息\"},{\"text\":\"<div class=\\\"text-color-orange mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">2</div>用Java8获取近N天日期\",\"link\":\"/categories/solutions/2021/11/18/用Java8获取近N天日期\"}],\"collapsed\":true}],\"/categories/tools/\":[{\"text\":\"<img class=\\\"chinese-zodiac\\\" style=\\\"position: static; vertical-align: middle; padding-bottom: 3px;\\\" src=\\\"/img/svg/chinese-zodiac/ox.svg\\\" title=\\\"牛年\\\" alt=\\\"生肖\\\">\\n 2021年 (5篇)\",\"items\":[{\"text\":\"<div class=\\\"text-color-red mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">1</div>Quartz 快速入门\",\"link\":\"/categories/tools/2021/03/10/Quartz快速入门\"},{\"text\":\"<div class=\\\"text-color-orange mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">2</div>Postman 快速入门\",\"link\":\"/categories/tools/2021/03/06/Postman快速入门\"},{\"text\":\"<div class=\\\"text-color-yellow mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">3</div>Another Redis Desktop Manager 快速入门\",\"link\":\"/categories/tools/2021/03/04/ARDM快速入门\"},{\"text\":\"<div class=\\\"text-color-gray mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">4</div>Redis Desktop Manager 快速入门\",\"link\":\"/categories/tools/2021/02/22/RDM快速入门\"},{\"text\":\"<div class=\\\"text-color-gray mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">5</div>初识 Lombok\",\"link\":\"/categories/tools/2021/01/14/初识Lombok\"}],\"collapsed\":false}],\"/courses/java/\":[{\"text\":\"Java语法入门 (14篇)\",\"items\":[{\"text\":\"<div class=\\\"text-color-red mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">1</div>开发环境搭建\",\"link\":\"/courses/java/01-Java语法入门/01-开发环境搭建\"},{\"text\":\"<div class=\\\"text-color-orange mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">2</div>第一个Java程序\",\"link\":\"/courses/java/01-Java语法入门/02-第一个Java程序\"},{\"text\":\"<div class=\\\"text-color-yellow mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">3</div>初识Eclipse\",\"link\":\"/courses/java/01-Java语法入门/03-初识Eclipse\"},{\"text\":\"<div class=\\\"text-color-gray mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">4</div>程序和计算机的那点事儿\",\"link\":\"/courses/java/01-Java语法入门/04-程序和计算机的那点事儿\"},{\"text\":\"<div class=\\\"text-color-gray mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">5</div>变量和常量\",\"link\":\"/courses/java/01-Java语法入门/05-变量和常量\"},{\"text\":\"<div class=\\\"text-color-gray mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">6</div>常用的运算符\",\"link\":\"/courses/java/01-Java语法入门/06-常用的运算符\"},{\"text\":\"<div class=\\\"text-color-gray mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">7</div>控制语句和流程图\",\"link\":\"/courses/java/01-Java语法入门/07-控制语句和流程图\"},{\"text\":\"<div class=\\\"text-color-gray mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">8</div>if选择结构\",\"link\":\"/courses/java/01-Java语法入门/08-if选择结构\"},{\"text\":\"<div class=\\\"text-color-gray mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">9</div>switch选择结构\",\"link\":\"/courses/java/01-Java语法入门/09-switch选择结构\"},{\"text\":\"<div class=\\\"text-color-gray mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">10</div>循环结构\",\"link\":\"/courses/java/01-Java语法入门/10-循环结构\"},{\"text\":\"<div class=\\\"text-color-gray mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">11</div>多重循环\",\"link\":\"/courses/java/01-Java语法入门/11-多重循环\"},{\"text\":\"<div class=\\\"text-color-gray mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">12</div>程序调试入门\",\"link\":\"/courses/java/01-Java语法入门/12-程序调试入门\"},{\"text\":\"<div class=\\\"text-color-gray mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">13</div>一维数组\",\"link\":\"/courses/java/01-Java语法入门/13-一维数组\"},{\"text\":\"<div class=\\\"text-color-gray mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">14</div>多维数组\",\"link\":\"/courses/java/01-Java语法入门/14-多维数组\"}],\"collapsed\":false},{\"text\":\"Java面向对象 (1篇)\",\"items\":[{\"text\":\"<div class=\\\"text-color-red mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">1</div>类和对象\",\"link\":\"/courses/java/02-Java面向对象/01-类和对象\"}],\"collapsed\":true},{\"text\":\"Java高级特性 (1篇)\",\"items\":[{\"text\":\"<div class=\\\"text-color-red mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">1</div>集合与泛型-1\",\"link\":\"/courses/java/03-Java高级特性/01-集合与泛型-1\"}],\"collapsed\":true},{\"text\":\"附录 (1篇)\",\"items\":[{\"text\":\"<div class=\\\"text-color-red mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">1</div>CentOS 8.2 安装 JDK 1.8.0_202\",\"link\":\"/courses/java/04-附录/01-CentOS安装JDK\"}],\"collapsed\":true}],\"/courses/mysql/\":[{\"text\":\"MySQL基础 (1篇)\",\"items\":[{\"text\":\"<div class=\\\"text-color-red mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">1</div>MySQL安装与配置\",\"link\":\"/courses/mysql/01-MySQL基础/01-MySQL安装与配置\"}],\"collapsed\":true},{\"text\":\"附录 (2篇)\",\"items\":[{\"text\":\"<div class=\\\"text-color-red mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">1</div>CentOS 8.2 安装 MySQL 5.7.39\",\"link\":\"/courses/mysql/03-附录/01-CentOS安装MySQL\"},{\"text\":\"<div class=\\\"text-color-orange mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">2</div>Docker 安装 MySQL 详细步骤\",\"link\":\"/courses/mysql/03-附录/02-Docker安装MySQL\"}],\"collapsed\":false}],\"/courses/mybatis/\":[{\"text\":\"MyBatis基础 (8篇)\",\"items\":[{\"text\":\"<div class=\\\"text-color-red mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">1</div>快速入门\",\"link\":\"/courses/mybatis/01-MyBatis基础/01-快速入门\"},{\"text\":\"<div class=\\\"text-color-orange mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">2</div>核心对象\",\"link\":\"/courses/mybatis/01-MyBatis基础/02-核心对象\"},{\"text\":\"<div class=\\\"text-color-yellow mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">3</div>核心配置文件\",\"link\":\"/courses/mybatis/01-MyBatis基础/03-核心配置文件\"},{\"text\":\"<div class=\\\"text-color-gray mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">4</div>SQL映射文件之查询元素\",\"link\":\"/courses/mybatis/01-MyBatis基础/04-SQL映射文件之查询元素\"},{\"text\":\"<div class=\\\"text-color-gray mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">5</div>SQL映射文件之增删改元素\",\"link\":\"/courses/mybatis/01-MyBatis基础/05-SQL映射文件之增删改元素\"},{\"text\":\"<div class=\\\"text-color-gray mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">6</div>SQL映射文件之自定义映射元素\",\"link\":\"/courses/mybatis/01-MyBatis基础/06-SQL映射文件之自定义映射元素\"},{\"text\":\"<div class=\\\"text-color-gray mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">7</div>SQL映射文件之缓存元素\",\"link\":\"/courses/mybatis/01-MyBatis基础/07-SQL映射文件之缓存元素\"},{\"text\":\"<div class=\\\"text-color-gray mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">8</div>动态SQL\",\"link\":\"/courses/mybatis/01-MyBatis基础/08-动态SQL\"}],\"collapsed\":false},{\"text\":\"MyBatis-Plus基础 (5篇)\",\"items\":[{\"text\":\"<div class=\\\"text-color-red mr-[6px]\\\" style=\\\"font-weight: 550; display: inline-block;\\\">1</div>快速入门\",\"link\":\"/courses/mybatis/02-MyBatis-Plus基础/01-快速入门\"},{\"text\":\"<div class=\\\"text-color-orange mr-[6px]\\\" style=\\\"font-weight: 550; 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