防止输入错误

Question

import java.util.Scanner;

public class test {

    public static void main(String[] args) {
        System.out.print("Enter a number: ");
        Scanner keyboard = new Scanner(System.in);
        int x = keyboard.nextInt();

    }
}

如何在输入int之前循环上面的代码，直到输入int而不是在输入非int时给出错误？

Answer 1

Scanner类内置了很多东西，除非你明确地想要捕获错误，否则你不需要做try-catches。

public static int test(){
    int number = 0;
    Scanner input = new Scanner(System.in);
    boolean valid = false;
    do{
        System.out.print("Please enter an integer: ");
        if(input.hasNextInt()){ // This checks to see if the next input is a valid **int**
            number = input.nextInt();
            valid = true;
        }
        else{
            System.out.print("Not a valid integer!\n");
            input.next();
        }
    }while(valid == false);
    return number;

}

Answer 2

这将尝试运行扫描仪，如果输入不是预期的输入，它将仅重新启动。您可以在其中添加一条消息，我的代码是为了简洁。

import java.util.Scanner;

public class test {

public static void main(String[] args) {
    System.out.print("Enter a number: ");
    Scanner keyboard = new Scanner(System.in);
    try {
        int x = keyboard.nextInt();
    }
    catch (java.util.InputMismatchException e) {
        main(null);
    }
}

}