How to convert a negative number to positive in Java

Java program to convert a negative number to positive:

In this post, we will learn how to convert a negative number to positive in Java. We can solve this in two different ways. The easiest way is to multiply the number by -1. We can also use the Math.abs method to find the absolute value, it changes a negative value to positive.

We will write a Java program that will take one negative number as input from the user and print out its positive value.

Method 1: By multiplying the number by -1:

In this method, we are multiplying a negative number by -1. It will give the positive value of that number. The program takes the number as input from the user and it also verifies if the number is a negative number or not.

Below is the complete program:

import java.util.Scanner;

public class FirstExample {

    public static void main(String[] args) {
        int givenNumber;
        int positiveNumber;

        try (Scanner sc = new Scanner(System.in)) {
            System.out.println("Enter a number: ");

            givenNumber = sc.nextInt();

            if (givenNumber < 0) {
                positiveNumber = givenNumber * (-1);
                System.out.println("Positive number: " + positiveNumber);
            } else {
                System.out.println("Please enter a positive number");
            }
        }

    }
}

Download it on GitHub

• The integer variable givenNumber is used to assign the user-input number. The second integer variable positiveNumber is used to assign the converted positive value of the number.
• It uses a Scanner object to read the user-input value. It assigns the user input value to the givenNumber variable.
• If the value of givenNumber is negative, it multiplies that value by -1 and assigns it to the integer variable positiveNumber and prints that value.

If you run this program, it will print output as below:

Enter a number: 
-23
Positive number: 23

Method 2: By using Math.abs():

The abs() is a static method defined in the Math class of Java. We can use this method to convert a negative number to positive. This method is defined as:

public static int abs(int a)

It returns the absolute value of a. If a is positive, it returns it. Else, it returns the negation value of a. The following program uses Math.abs() to convert a negative number to positive:

import java.util.Scanner;

public class SecondExample {

    public static void main(String[] args) {
        int givenNumber;
        int positiveNumber;

        try (Scanner sc = new Scanner(System.in)) {
            System.out.println("Enter a number: ");

            givenNumber = sc.nextInt();

            if (givenNumber < 0) {
                positiveNumber = Math.abs(givenNumber);
                System.out.println("Positive number: " + positiveNumber);
            }
        }

    }
}

Download it on GitHub

It will give similar output.

How to use Math.abs with double:

The above two examples uses integer values with the Math.abs method. We can also use float, double or long as the parameter. The Math.abs method is defined for all of these types:

public static long abs(long a){}

public static float abs(float a){}

public static double abs(double a){}

The following example shows how to use the Math.abs() method with a double parameter:

import java.util.Scanner;

public class ThirdExample {

    public static void main(String[] args) {
        double givenNumber;
        double positiveNumber;

        try (Scanner sc = new Scanner(System.in)) {
            System.out.println("Enter a number: ");

            givenNumber = sc.nextDouble();

            if (givenNumber < 0) {
                positiveNumber = Math.abs(givenNumber);
                System.out.println("Positive number: " + positiveNumber);
            } else {
                System.out.println("Please enter a negative number.");
            }
        }

    }
}

Download it on GitHub

If you run this program, it will print output as below:

Enter a number: 
-23.5576
Positive number: 23.5576

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