问Java编程练习？

EN

import java.util.Scanner;
public class Test {

    public static void main(String[] args) {

        Scanner input = new Scanner(System.in);
        Random generator = new Random();
        int num1 = generator.nextInt(9)+1;
        int num2 = generator.nextInt(9)+1;
        int num3 = generator.nextInt(9)+1;
        int num4 = generator.nextInt(9)+1;
        int right = 0;

        num1 = num1*1000;
        num2 = num2*100;
        num3 = num3*10;
        int code = num1 + num2 + num3 + num4;
        System.out.println("Lets play High-Low");
        while(right == 0){
            System.out.println("Guess a four digit number");
        int guess = input.nextInt();

        if (guess < code){
            System.out.println("Low!");
            }
            else if (guess > code){
            System.out.println("High!");
            }
            else if (guess == code){
            System.out.println("You win! The code was " + code + "!");
            right = 1;
            }

        }

    }
}