Java Program to Check if a Number is Positive or Negative

In this section, we will explore Java programs to determine whether a number is positive or negative. We will employ the following approaches to check the number’s sign:

• Using Relational Operator
• Using Math.signum() Method
• Using Integer.signum() Method
• Using Bit Shift Operator
• Using ArrayList class

Using Relational Operator

To determine whether a number is positive or negative, we have implemented the following logic in our Java program.

• If the number>0 the number is positive.
• If the number<0 the number is negative.
• If a number is neither positive nor negative, the number is equal to 0.

In the provided program, we have initialized a number and utilized the if-else statement to determine whether the number is positive or negative.

CheckPositiveOrNegativeExample.java

public class CheckPositiveOrNegativeExample  
{  
public static void main(String[] args)   
{  
//number to be check  
int num=912;  
//checks the number is greater than 0 or not  
if(num>0)  
{  
System.out.println("The number is positive.");  
}  
//checks the number is less than 0 or not  
else if(num<0)  
{  
System.out.println("The number is negative.");  
}  
//executes when the above two conditions return false  
else  
{  
System.out.println("The number is zero.");  
}  
}  
}

Output:

The number is positive.

In the given program, we prompt the user to enter a number. Subsequently, we employ the if-else statement to determine whether the provided number is positive or negative.

CheckPositiveOrNegativeExample1.java

import java.util.Scanner;  
public class CheckPositiveOrNegativeExample1  
{  
public static void main(String[] args)   
{  
int num;  
//object of the Scanner class  
Scanner sc = new Scanner(System.in);  
System.out.print("Enter a number: ");  
//reading a number from the user  
num = sc.nextInt();  
//checks the number is greater than 0 or not  
if(num>0)  
{  
System.out.println("The number is positive.");  
}  
//checks the number is less than 0 or not  
else if(num<0)  
{  
System.out.println("The number is negative.");  
}  
//executes when the above two conditions return false  
else  
{  
System.out.println("The number is zero.");  
}  
}  
}

Output 1:

Enter a number: 23
The number is positive.

Output 2:

Enter a number: -499
The number is negative.

Output 3:

Enter a number: 0
The number is zero.

Using Math.signum() Method

There is an alternative method to check whether a number is positive or negative. In Java, the Math class offers the signum() method specifically for this purpose. The signum() method is a static method that takes a double-type parameter.

Syntax:

public static double signum(double d)

The signum() method returns the signum function of the argument, as described below:

• 0.0: if the argument is 0.
• 1.0: if the argument is greater than 0.
• -1.0: if the argument is less than 0.

Special Cases:

NaN: if the argument is NaN.

Argument: if the argument is positive or negative zero.

Additionally, the Math class provides an overloaded version of the signum() method that accepts a float value instead of a double.

Syntax:

public static float signum(float f)

CheckPositiveOrNegativeExample2.java

import java.util.Scanner;  
import java.lang.Math.*;  
public class CheckPositiveOrNegativeExample2  
{  
public static void main(String[] args)   
{  
double num, result;  
//object of the Scanner class   
Scanner sc = new Scanner(System.in);  
System.out.print("Enter a number you want to check: ");  
//reading an input from the user  
num = sc.nextDouble();  
//invoking signum() method of the Math class  
result=Math.signum(num);  
//print the result  
System.out.print(result);  
}  
}

Output:

Enter a number you want to check: -98.6
-1.0

Using Integer.signum() Method

The Java Integer class also includes the signum() method, which serves the purpose of checking whether a number is positive or negative. This static method accepts an integer-type parameter.

Syntax:

public static int signum(int i)

The signum() method of the Integer class returns the signum function of the provided argument ‘i’ according to the following rules:

• 0: if the argument is 0.
• 1: if the argument is greater than 0.
• -1: if the argument is less than 0.

CheckPositiveOrNegativeExample3.java

import java.util.Scanner;  
import java.lang.Integer.*;  
public class CheckPositiveOrNegativeExample3  
{  
public static void main(String[] args)   
{  
int num, result;  
//object of the Scanner class  
Scanner sc = new Scanner(System.in);  
System.out.print("Enter a number you want to check: ");  
//taking an integer value from the user  
num = sc.nextInt();  
//invoking signum() method of the Integer class  
result=Integer.signum(num);  
//prints the result  
System.out.print(result);  
}  
}

Output 1:

Enter a number you want to check: 99
1

Output 2:

Enter a number you want to check: -99
-1

Output 3:

Enter a number you want to check: 0
0

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