重新運行程序終止

Question

我有這樣的代碼

public static void main(String[] args) { 
    Scanner scanner = new Scanner(System.in); 
    System.out.println("Enter menu number: "); 
    int value = scanner.nextInt(); 

    if (value == 1){ 
     System.out.println("first"); 
    } else if (value == 2) { 
     System.out.println("second"); 
    } else if (value == 3) { 
     System.out.println("third"); 
    } else { 
     System.out.println("closing program"); 
    }    
} 

我想要的行爲是「1」時輸入的菜單值和「第一」被打印出來，程序不會終止，但追溯到System.out.println("Enter menu number: ");，因此可以輸入另一個菜單編號等。不知道該怎麼去做。

Answer 1

你可以做這樣的事情

public static void main(String[] args) { 
    Scanner scanner = new Scanner(System.in); 
    String userInput = ""; 
    while (true) { 
     System.out.println("Enter menu number: "); 
     userInput = scanner.next(); 
     if (userInput.trim().toUpperCase().equals("EXIT")) { 
      break; 
     } 
     int value = Integer.parseInt(userInput); 

     if(value == 1){ 
      System.out.println("first"); 
     } 
     else if(value==2){ 
      System.out.println("second"); 
     } 
     else if(value==3){ 
      System.out.println("third"); 
     } 

    }    
} 

Answer 2

把你的代碼的循環：

public static void main(String[] args) { 
    Scanner scanner = new Scanner(System.in); 
    int value = -1; 

    do { // Here you will loop until you enter something to "terminate" 
    System.out.println("Enter menu number: "); 
    value = scanner.nextInt(); 

    if (value == 1){ 
     System.out.println("first"); 
    } else if (value==2){ 
     System.out.println("second"); 
    } else if(value==3){ 
     System.out.println("third"); 
    } else{ 
     System.out.println("closing program"); 
    } 
    } while (value != -1); // End condition 
}