Java中switch的三种用法方式

switch (flag){

​ case 0 : 语句一； break；

​ case 1: 语句二； break；

​ default: 语句n; break;

}

int flag = 3;
switch (flag){
  
 case 0: System.out.println("The number is 0" ); break;
 case 1: System.out.println("The number is 1" ); break;
 case 2: System.out.println("The number is 2" ); break;
 default: System.out.println("you are right" ); break;
}

int flag = 3;
switch (flag){
    
  case 0 -> System.out.println("The number is 0" ); 
  case 1 -> System.out.println("The number is 1" ); 
  case 2 -> System.out.println("The number is 2" ); 
  default -> System.out.println("you are right" ); 
}

int flag = 2;
String ss;
ss = switch (flag){
   case 0 -> "The number is 0" ;
   case 1 -> "The number is 1" ;
   case 2 -> {
       String c = "The number is 2";
       yield c;
      }
   default -> "you are right" ;
 };
System.out.println(ss);

import java.util.HashMap;
import java.util.Random;
import java.util.Scanner;

public class test {
  private HashMap<Integer, String> game = new HashMap<Integer, String>();

  public test() {
    game.put(1, "石头");
    game.put(2, "剪刀");
    game.put(3, "步");
  }

  public void randomGame() {

    Scanner in = new Scanner(System.in);
    System.out.println("这是一个石头剪刀布的游戏\n" +
        "我们学着使用 switch 语法 来完成这个小游戏程序！ \n" +
        "Let me start!");

    int num = 3;
    boolean flag = true;
    int win = 0;
    while (flag) {
      System.out.print("机器人已经准备好：\n请输入你的操作 如：石头\n输入:");
      String myHand = in.next();
      String robot = getRobot();
      String s = "你的出招为 " + myHand + " 机器人的出招为 "
          + robot;
      // 先判断相同情况下
      if (robot.equals(myHand)) {
        System.out.println(s+ "平局!"); }
      // 判断不同情况下
      else if ( myHand.equals("剪刀"))
      {
        switch (robot){
          case "石头" -> System.out.println(s + " you lose");
          case "布" -> {
            System.out.println(s + " you win");
            win += 1;
          }
        }
      }else if (myHand.equals("石头")){
        switch (robot) {
          case "剪刀" -> System.out.println(s + " you lose");
          case "布" -> {
            System.out.println(s + " you win");
            win += 1;
          }
        }
      }else if (myHand.equals("布")){
        switch (robot) {
          case "剪刀" -> System.out.println(s + " you lose");
          case "石头" -> {
            System.out.println(s + " you win");
            win += 1;
          }
        }
      }else {
        System.out.println("你输入的" + myHand + "是错误的");
      }
      num-=1;
      if (num == 0){flag = false;}
      System.out.println("你还有" + num + "次机会.");

    }
    System.out.println("三局比赛中， 你一共获胜次数为 " + win);
  }

  public String getRobot() {
    // 得到机器人的出招
    int count = (int) (Math.random() * 10 / 3);
    if (count > 0){
      return game.get(count);
    }else {
      return game.get(count + 1);
    }
  }

  public static void main(String[] args) {
    test me = new test();
    me.randomGame();
  }
}
    return game.get(count);
  }else {
    return game.get(count + 1);
  }
}

public static void main(String[] args) {
  test me = new test();
  me.randomGame();
}

}