section.java.controlflow.xml

<?xml version="1.0" encoding="UTF-8"?>
<chapter id="ControlFlow">
	<title>流程控制</title>
	<section>
		<title>Switch</title>
		<section>
			<title>yield</title>
			<programlisting>
			<![CDATA[
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);

	}

}			
			]]>
			</programlisting>
			<para>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</para>
			<programlisting>
			<![CDATA[
		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);			
			]]>
			</programlisting>
			<programlisting>
			<![CDATA[
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
    }

}
			
			]]>
			</programlisting>
		</section>
	</section>
</chapter>