1. Java8 和 Java21
Java8 引入字符串和枚举
Java21 可以返回值, yield关键字, switch 表达式, 模式匹配, null值处理
2. 代码案例
1. Java8
public static void java8() {String day = "tuesday";switch (day) {case "monday":System.out.println("work");break;case "tuesday":System.out.println("work");break;case "saturday":System.out.println("day off");break;case "sunday":System.out.println("day off");break;}//枚举值monday,tuesday,wednesday,thursday,friday,saturday,sunday;Days days = Days.saturday;switch (days) {case Days.monday:System.out.println("work");break;case Days.tuesday:System.out.println("work");break;case Days.saturday:System.out.println("day off");break;case Days.sunday:System.out.println("day off");break;}}
运行结果
2. Java21
public static String java21() {//null 处理var name = switch (getName()) {case "" -> "";case "1" -> "num";case null -> "null";default -> "unknown";};System.out.println(name);//模式匹配Object o = 1;Object a = switch (o) {case Integer i -> 1 + i;case String s -> "1" + s;default -> o.toString();};System.out.println(a);//yield ， 表达式String day = "sunday";return switch (day) {case "monday", "tuesday" -> "work";case "saturday", "sunday" -> {System.out.println("day off");yield "work";}default -> "unknown";};}static String getName() {return null;}
运行结果
