Java - 检查输入是否为正整数、负整数、自然数等。
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Java - Check if input is a positive integer, negative integer, natural number and so on.
提问by kar
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.
Java 中是否有任何内置方法可以让您找到用户输入的类型，无论是正数还是负数等等？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。
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.");
}
}
采纳答案by Juned Ahsan
If you really have to avoid operators then use Math.signum()
如果您真的必须避免使用运算符，请使用Math.signum()
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.
返回参数的符号函数；如果参数为零，则为零，如果参数大于零，则为 1.0，如果参数小于零，则为 -1.0。
EDIT : As per the comments, this works for only double and float values. For integer values you can use the method:
编辑：根据评论，这仅适用于 double 和 float 值。对于整数值，您可以使用以下方法：
回答by blackpanther
What about using the following:
如何使用以下内容：
int number = input.nextInt();
if (number < 0) {
// negative
} else {
// it's a positive
}
回答by Theolodis
You could use if(number >= 0). The fact that you use int number = input.nextInt();makes sure that it has to be an Integer.
你可以使用if(number >= 0). 您使用的事实int number = input.nextInt();确保它必须是一个整数。
回答by Prabhakaran Ramaswamy
Use like below code.
使用如下代码。
if(number >=0 ) {
System.out.println("Number is natural and positive.");
}
回答by Juned Ahsan
(You should you as Else-Ifstatement to check the for the three different state (positive, negative, 0)
（你应该作为Else-If语句来检查三种不同的状态（正、负、0）
Here is a simple example (excludes the possibility of non-integer values)
这是一个简单的例子（排除非整数值的可能性）
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 == 0)
{ System.out.println("Number is equal to zero"); }
else if (number > 0)
{ System.out.println("Number is positive"); }
else
{ System.out.println("Number is negative"); }
}
}
回答by Kefirchiks
For integers you can use Integer.signum()
对于整数，您可以使用Integer.signum()
Returns the signum function of the specified int value. (The return value is -1 if the specified value is negative; 0 if the specified value is zero; and 1 if the specified value is positive.)
返回指定 int 值的符号函数。（如果指定值为负，则返回值为 -1；如果指定值为 0，则返回值为 0；如果指定值为正，则返回值为 1。）
