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<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>第 4 章 流程控制</title><link rel="stylesheet" type="text/css" href="../docbook.css" /><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot" /><link rel="home" href="../index.html" title="Netkiller Java 手札（版）" /><link rel="up" href="index.html" title="部分 I. Java 21" /><link rel="prev" href="type/java.boolean.html" title="3.13. 布尔型 Boolean" /><link rel="next" href="class/index.html" title="第 5 章 面向对象" /></head><body><a xmlns="" href="//www.netkiller.cn/">Home</a> | <a xmlns="" href="//netkiller.github.io/">简体中文</a> | <a xmlns="" href="http://netkiller.sourceforge.net/">繁体中文</a> | <a xmlns="" href="/journal/index.html">杂文</a>
| <a xmlns="" href="https://github.com/netkiller">Github</a> | <a xmlns="" href="https://zhuanlan.zhihu.com/netkiller">知乎专栏</a> | <a xmlns="" href="https://www.facebook.com/bg7nyt">Facebook</a> | <a xmlns="" href="http://cn.linkedin.com/in/netkiller/">Linkedin</a> | <a xmlns="" href="https://www.youtube.com/user/bg7nyt/videos">Youtube</a> | <a xmlns="" href="//www.netkiller.cn/home/donations.html">打赏(Donations)</a> | <a xmlns="" href="//www.netkiller.cn/home/about.html">About</a><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">第 4 章 流程控制</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="type/java.boolean.html">上一页</a> </td><th width="60%" align="center">部分 I. Java 21</th><td width="20%" align="right"> <a accesskey="n" href="class/index.html">下一页</a></td></tr></table><hr /></div><table xmlns=""><tr><td><iframe src="//ghbtns.com/github-btn.html?user=netkiller&repo=netkiller.github.io&type=watch&count=true&size=large" height="30" width="170" frameborder="0" scrolling="0" style="width:170px; height: 30px;" allowTransparency="true"></iframe></td><td><iframe src="//ghbtns.com/github-btn.html?user=netkiller&repo=netkiller.github.io&type=fork&count=true&size=large" height="30" width="170" frameborder="0" scrolling="0" style="width:170px; height: 30px;" allowTransparency="true"></iframe></td><td><iframe src="//ghbtns.com/github-btn.html?user=netkiller&type=follow&count=true&size=large" height="30" width="240" frameborder="0" scrolling="0" style="width:240px; height: 30px;" allowTransparency="true"></iframe></td><td></td><td><a href="https://zhuanlan.zhihu.com/netkiller"><img src="/images/logo/zhihu-card-default.svg" height="25" /></a></td><td valign="middle"><a href="https://zhuanlan.zhihu.com/netkiller">知乎专栏</a></td><td></td><td></td><td></td><td></td></tr></table><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a id="ControlFlow"></a>第 4 章 流程控制</h2></div></div></div><div class="toc"><p><strong>目录</strong></p><dl class="toc"><dt><span class="section"><a href="ControlFlow.html#id814">4.1. Switch</a></span></dt><dd><dl><dt><span class="section"><a href="ControlFlow.html#id813">4.1.1. yield</a></span></dt></dl></dd></dl></div>
<div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="id814"></a>4.1. Switch</h2></div></div></div>
<div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="id813"></a>4.1.1. yield</h3></div></div></div>
<pre class="programlisting">
package cn.netkiller.demo;
public class DemoSwitch {
public DemoSwitch() {
}
public static void main(String[] args) {
var number = 4;
var operation = "平方";
var result = switch (operation) {
case "立方" -> {
yield number * number * number;
}
case "平方" -> {
yield number * number;
}
default -> number;
};
System.out.println(result);
}
}
</pre>
<p>不必为break每个 case 块定义一个语句，我们可以简单地使用箭头语法</p>
<pre class="programlisting">
int money = 3;
String cn = switch (money) {
case 1 -> "壹";
case 2 -> "贰";
case 3 -> "叁";
case 4 -> "肆";
case 5 -> "伍";
case 6 -> "陆";
case 7 -> "柒";
case 8 -> "捌";
case 9 -> "玖";
case 10 -> "拾";
default -> "零";
};
System.out.println(cn);
</pre>
<pre class="programlisting">
package cn.netkiller.test;
public class Test {
public static void main(String[] args) {
withSwitchExpression(Fruit.APPLE);
withReturnValue(Fruit.AVOCADO);
withYield(Fruit.VEGETABLES);
}
private static void withSwitchExpression(Fruit fruit) {
switch (fruit) {
case APPLE, PEAR -> System.out.println("普通水果");
case MANGO, AVOCADO -> System.out.println("进口水果");
default -> System.out.println("未知水果");
}
}
private static void withReturnValue(Fruit fruit) {
System.out.println(switch (fruit) {
case APPLE, PEAR -> "普通水果";
case MANGO, AVOCADO -> "进口水果";
default -> "未知水果";
});
}
private static void withYield(Fruit fruit) {
String text = switch (fruit) {
case APPLE, PEAR, MANGO, AVOCADO -> {
System.out.println("水果: " + fruit);
yield "水果: " + fruit;
}
case VEGETABLES -> {
System.out.println("蔬菜: " + fruit);
yield "蔬菜：" + fruit;
}
default -> {
yield "未知食物";
}
};
System.out.println(text);
}
public enum Fruit {
APPLE, PEAR, MANGO, AVOCADO, VEGETABLES
}
}
</pre>
</div>
</div>
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