`Math.abs`, absolute value

Consider the number -1. It has an absolute part—the value 1. With Math.abs we take this absolute value, making the number positive.

With logical tests, we can check for negative and positive numbers. But Math.abs streamlines this. It makes some programs simpler and easier to reason about.

Absolute value

To start, an absolute value is the number with no negative sign. If the number is already positive, no change is made. We first import java.lang.Math.

Detail Math.abs returns various types. These depend on the types passed to it. If we pass an int, we receive an int in return.

import java.lang.Math;

public class Program {
    public static void main(String[] args) {

        // This version uses an int.
        int value = Math.abs(-1);
        System.out.println(value);

        // This version uses a double.
        double value2 = Math.abs(-1.23);
        System.out.println(value2);

        int value3 = Math.abs(1);
        System.out.println(value3);
    }
}1
1.23
1

Rewrite `if`-statement

Sometimes we have logic that acts on positive and negative numbers in different ways. This can be rewritten with Math.abs in certain programs.

Here The addAbsoluteValue adds if a number is positive, and subtracts if it is negative.

Tip We can rewrite addAbsoluteValue with a call to Math.abs. This reduces code size and makes things clearer.

public class Program {

    static int addAbsoluteValue(int base, int number) {
        // Add number if it is positive.
        // ... Subtract if it is negative.
        if (number > 0) {
            return base + number;
        } else {
            return base - number;
        }
    }

    public static void main(String[] args) {

        // Use our custom method and rewrite it with Math.abs.
        int result1 = addAbsoluteValue(5, -1);
        int result2 = addAbsoluteValue(5, 10);
        int result3 = 5 + Math.abs(-1);
        int result4 = 5 + Math.abs(10);

        System.out.println(result1);
        System.out.println(result2);
        System.out.println(result3);
        System.out.println(result4);
    }
}6
15
6
15

Overloads

In Java 8 we find overloaded versions of Math.abs for double, float, int and long. For values like byte and short, we can use the int overload.

Performance

In my tests, the performance of Math.abs is similar to an if-statement. I could not demonstrate any important differences.

A summary

With Math.abs we can simplify logic with a method call. This is simpler than an if-statement or other logical test. It leads to clearer programs, ones easier to comprehend.