java - 我怎样才能让这段代码继续下去，直到选择正确的答案？

Question

我希望这段代码继续执行，直到输入可接受的答案(即1,2,3,4)，但我不知道如何做到这一点。谢谢。另外，如果有任何其他方法可以简化此操作，也会有所帮助。

import java.util.Scanner;
public class NewMain {
    public static void main(String[] args) {
        String input;
        Scanner keyboard =  new Scanner(System.in);

        System.out.println("Your choice\n[1]Up \n[2]Down \n[3]Left \n[4]Right");
        input = keyboard.nextLine();

        if(input.equals("1")) {
            System.out.println("You are going up!!!");
        }
        else {
            if(input.equals("2")){
                System.out.println("You are going down!!!");
            }
            else {
                if(input.equals("3")) {
                    System.out.println("You are going left!!!");
                }
                else {
                    if(input.equals("4")) {
                        System.out.println("You are going right!!!");
                    }
                    else{}
                }
            }
        }
    }
}

Answer 1

尝试使用开关盒 http://docs.oracle.com/javase/tutorial/java/nutsandbolts/switch.html

您的案例:

while(flag == false){

    switch (imput) {
        case "1":         
        System.out.println("You are going up!!!"); flag=true;
        break;

        case "2":  
        System.out.println("You are going down!!!"); flag = true;
        break;

        case "3":  
        System.out.println("You are going left!!!"); flag = true;
        break;

        case "4":   System.out.println("You are going right!!!"); flag = true;
        break;
    }

}

您可以输入可选条件默认: