java IF NOT语句

Question

import java.util.Random;
import java.util.Scanner;

public class Game {
    public static void main(String[] args) {

        System.out.println("Guess a number betwwen 1 and 1000");

        Random rand = new Random(); 
        int secretNumber = rand.nextInt (1000);


        Scanner keyboard = new Scanner(System.in);
        int guess;

        do {
        guess = keyboard.nextInt();

        if (guess == secretNumber)
            System.out.println("You WON!!! Congratulations!");
        else if (guess < secretNumber)
             System.out.println("Nope, to low");
        else if (guess > secretNumber)
            System.out.println("Sorry, to high");


        } while (guess != secretNumber);


    }
}

我怎样才能在这段代码中添加一条语句，如果不是数字输入系统的话。出来println（“无效输入，请仅使用类型号！”）

Answer 1

public class Game {
    public static void main(String[] args) {

    System.out.println("Guess a number betwwen 1 and 1000");

    Random rand = new Random(); 
    int secretNumber = rand.nextInt (1000);


    Scanner keyboard = new Scanner(System.in);
    int guess;

    do {
    if (!keyboard.hasNextInt()) {
        System.out.println("invalid input, please use type numbers only!");
        return;
    }
    guess = keyboard.nextInt();

    if (guess == secretNumber)
        System.out.println("You WON!!! Congratulations!");
    else if (guess < secretNumber)
         System.out.println("Nope, to low");
    else if (guess > secretNumber)
        System.out.println("Sorry, to high");


    } while (guess != secretNumber);


    }
}

Answer 2

扫描仪。nextInt（）抛出 InputMismatchException如果下一个标记与整数正则表达式不匹配，或者超出范围

所以你应该把你的代码包装成一个试一试的过程，记住这一点

Answer 3

我想你应该把下面的内容包装在guess=键盘上。nextInt（）：

 try  
 {  
     guess = keyboard.nextInt()
     Integer.parseInt(guess);  

     <your if statements>

  } catch(Exception ex)  
  {  
    System.out.println("Your comment");
  }  

Answer 4

可以在循环中添加一个try-catch块

  do {
  try{
    guess = keyboard.nextInt();

    if (guess == secretNumber)
        System.out.println("You WON!!! Congratulations!");
    else if (guess < secretNumber)
         System.out.println("Nope, to low");
    else if (guess > secretNumber)
        System.out.println("Sorry, to high");
    }
catch(InputMismatchException e){
System.out.prinln("Not a number");
}


    } while (guess != secretNumber);