如何在 Java 的 Switch 语句中使用字符串

Question

当我运行代码时，我的输入字符串不会出现。 首先它说当我在我的 Main 方法中使用它时它无法使用。 在我将它从我的 Main 方法中取出并将它放在 Public 类中之后，无法使用的问题就消失了。 但是在运行代码时它仍然不会出现。

public class Number0to9 {    
  public static String input;

  public static void main(String[] args) {        
    tryagain: while (true) {
      System.out.print("Type a number between 0 and 9 : ");

      Scanner scan = new Scanner(System.in);          
      int x = scan.nextInt();
      int output = x;
      input = "You entered number: ";

      switch (x) {
        case 0:
          input += output;
          break tryagain;
        case 1:
          input += output;
          break tryagain;
        case 2:
          input += output;
          break tryagain;
        case 3: 
          input += output;
          break tryagain;
        case 4:
          input += output;
          break tryagain;
        case 5: 
          input += output;
          break tryagain;
        case 6: 
          input += output;
          break tryagain;
        case 7:
          input += output;
          break tryagain;
        case 8:
          input += output;
          break tryagain;
        case 9:
          input += output;
          break tryagain;
        default:
          System.out.println("Your number was bigger than 9");
          break;
      }   
    }        
  } 
} 

Answer 1

应该是这样的？

public static void main(String[] args) {
        boolean digitEntered = false;
        String input = "You enetred number : ";
        while (digitEntered == false) {
            System.out.print("Type a number between 0 and 9 : ");
            Scanner scan = new Scanner(System.in);
            int x = scan.nextInt();

            if (x >= 0 && x <= 9) {
                digitEntered = true;
                input += x;
            } else {
                System.out.println("Your number was bigger than 9 ");

            }
        }
        System.out.println(input);
    }

Answer 2

用于终止标记循环的 Java break 语句。 并且您的 String input包含其中的值。 尝试在 while 循环后访问它。

public class Number0to9 {

    public static String input;

    public static void main(String[] args) {

    tryagain : while (true) {
    System.out.print("Type a number between 0 and 9 : ");
    Scanner scan = new Scanner(System.in);
    int x = scan.nextInt();
    int output = x;
    input = "You enetred number : ";


    switch (x) {
        case 0:
            input += output;
                break tryagain;
        case 1:
            input += output;
                break tryagain;
        case 2:
            input += output;
                break tryagain;
        case 3: 
            input += output;
                break tryagain;
        case 4:
            input += output;
                break tryagain;
        case 5: 
            input += output;
                break tryagain;
        case 6: 
            input += output;
                break tryagain;
        case 7:
            input += output;
                break tryagain;
        case 8:
            input += output;
                break tryagain;
        case 9:
            input += output;
                break tryagain;
        default:
                System.out.println("Your number was bigger than 9 ");
            break;
    }   
    }
System.out.println(input);
} 
} 

Answer 3

input += output;

只有当两个变量都是 int（或任何其他算术变量类型）时，上述代码语句才能用于添加输入和输出。

如果要连接输入和输出，首先要将输出转换为字符串。

input = input + Integer.toString(output);

在每种情况下进行此更改。