switch表达式新语法

左手的ㄟ右手 2024-03-26 19:59 70阅读 0赞

**1、JDK12之前的原语法**

public static void choiceSwitch(int num) {       
            switch (num) {
                case 1:
                    System.out.println("春");
                    break;
                case 2:
                    System.out.println("夏");
                    break;
                default:
                    break;
            }
    }

代码**冗余**，每处都要加break；

**2、箭头操作符**

String srt = switch (num) {
                case 1 -> "春";
                case 2 -> "夏";
                default -> "";
            };
            System.out.println(srt);

新语法只会执行匹配语句，没有穿透性，所以**不用写break**；

可以**返回一个值**

switch (num) {
                case 1 -> {System.out.println("春");
                System.out.println("春天");}
                case 2 -> System.out.println("夏");
                default -> System.out.println("");
            };
            System.out.println(srt);

但是，**多条语句**需要\{ \} 括起来

**3、yield 关键字**

String str = switch (num) {
                case 1 :
                    yield "春天";
                case 2 :
                    yield "夏天";
                default: 
                    yield " ";
            };

利用yield将值返回，类似于[ return][return]

String str = switch (num) {
                case 1 -> {
                    System.out.println("春");
                    yield "春天";
                }
                case 2 -> {
                    System.out.println("夏");
                    yield "夏天";
                }
                default-> {
                    System.out.println(" ");
                    yield " ";
                }
                
            };

多条语句\{ \}起来

[return]: https://blog.csdn.net/m0_74421344/article/details/128227100?ops_request_misc=%257B%2522request%255Fid%2522%253A%2522167837904716800184121352%2522%252C%2522scm%2522%253A%252220140713.130102334.pc%255Fblog.%2522%257D&request_id=167837904716800184121352&biz_id=0&utm_medium=distribute.pc_search_result.none-task-blog-2~blog~first_rank_ecpm_v1~rank_v31_ecpm-1-128227100-null-null.blog_rank_default&utm_term=%E8%BF%94%E5%9B%9E%E7%B1%BB%E5%9E%8B&spm=1018.2226.3001.4450