Java-检查输入是否为正整数，负整数，自然数等. [英] Java - Check if input is a positive integer, negative integer, natural number and so on.

问题描述

Java中是否有任何内置方法，您可以在其中找到用户输入的类型，无论是正输入还是负输入等等?下面的代码不起作用.我试图找到一种方法来输入任何可以在if语句中执行的内置方法.

Is there any in-built method in Java where you can find the user input's type whether it is positive, or negative and so on? The code below doesn't work. I am trying to find a way to input any in-built method that can do it at the if statement.

import java.util.Scanner;

public class Compare {

    public static void main(String[] args) { 

        Scanner input = new Scanner(System.in);

        System.out.print("Enter a number: ");
        int number = input.nextInt();

        if(number == int) 
            System.out.println("Number is natural and positive.");
    }
}

推荐答案

如果您真的必须避免使用运算符，请使用

If you really have to avoid operators then use Math.signum()

返回参数的正则函数；如果参数为零零，如果自变量大于零，则为1.0，如果自变量大于-1.0，则为-1.0小于零.

Returns the signum function of the argument; zero if the argument is zero, 1.0 if the argument is greater than zero, -1.0 if the argument is less than zero.

根据注释，这仅适用于double和float值.对于整数值，可以使用以下方法:

EDIT : As per the comments, this works for only double and float values. For integer values you can use the method:

Integer.signum(inti)

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