Java如何在switch语句下中断switch循环？

Question

我有一个家庭作业来实现一个简单的测试应用程序，下面是我的当前代码：

import java.util.*;

public class Test{

private static int typing;

public static void main(String argv[]){
    Scanner sc = new Scanner(System.in);
    System.out.println("Testing starts");
    while(sc.hasNextInt()){
        typing = sc.nextInt();
        switch(typing){
            case 0:
              break; //Here I want to break the while loop
            case 1:
              System.out.println("You choosed 1");
              break;
            case 2:
              System.out.println("You choosed 2");
              break;
            default:
              System.out.println("No such choice");
        }
    }
      System.out.println("Test is done");
    }
}

我现在想做的是，当0被按下时，它意味着用户想要退出测试，然后我破坏while loop并打印Test is done，但是它不是那样工作的，我知道原因可能是"break"破坏了switch，我怎么能让它破坏while loop呢？

Answer 1

您可以label自己的while循环，并break labeled loop，它应该如下所示：

loop: while(sc.hasNextInt()){
    typing = sc.nextInt();
    switch(typing){
        case 0:
          break loop; 
        case 1:
          System.out.println("You choosed 1");
          break;
        case 2:
          System.out.println("You choosed 2");
          break;
        default:
          System.out.println("No such choice");
    }
}

label可以是您想要的任何单词，例如"loop1"。

Answer 2

您需要一个布尔变量，例如shouldBreak。

    boolean shouldBreak = false;
    switch(typing){
        case 0:
          shouldBreak = true;
          break; //Here I want to break the while loop
        case 1:
          System.out.println("You choosed 1");
          break;
        case 2:
          System.out.println("You choosed 2");
          break;
        default:
          System.out.println("No such choice");
    }
    if (shouldBreak) break;

Answer 3

将时间放在函数中，当您按0而不是换行时，只需return。例如：

    import java.util.*;

public class Test{

private static int typing;

public static void main(String argv[]){
    Scanner sc = new Scanner(System.in);
    func(sc);
      System.out.println("Test is done");
    }
}

public static void func(Scanner sc) {


    System.out.println("Testing starts");
    while(sc.hasNextInt()){
        typing = sc.nextInt();
        switch(typing){
            case 0:
              return; //Here I want to break the while loop
            case 1:
              System.out.println("You choosed 1");
              break;
            case 2:
              System.out.println("You choosed 2");
              break;
            default:
              System.out.println("No such choice");
        }
    }
}

}