hasNextInt()在Java中的用法 [英] Usage of hasNextInt() in java

问题描述

我是一个初学者，对使用hasNextInt()感到困惑.如果它检查了输入，那么我们不应该之后使用它吗?但是，在下面的给定代码中，它与if语句一起使用.请指教.

I am a beginner and I am confused with using hasNextInt(). If it checks the input, then shouldn't we be using it after asking the user for input? However, in the given code below, it is used with if statement. Please advise.

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

        System.out.println("Enter your number");
        if (userInput.hasNextInt()) {
            int numberEntered = userInput.nextInt();
            System.out.println("You entered an integer");
        } else {
            System.out.println("you didn't enter an integer");
        }
    }
}

推荐答案

您可以使用它来测试用户的输入，因此可以确保在调用nextInt时不会出现异常，因为输入不是int，这也不会使他的光标向前移动:

You use it to test the user's input, so you are sure that when you call nextInt you won't have an exception because the input wasn't an int, it's also not moving he cursor forward:

Scanner scanner = new Scanner(System.in);
if(scanner.hasNextInt()){
    System.out.println(scanner.nextInt());
}

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