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# Java - Math.abs() method example

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The `Math.abs()` function returns the absolute value of a number.

The absolute value of the number x denoted |x|, is the non-negative value of x without regard to its sign.

Popular usage examples:

``````public class MathExample {

public static void main(String[] args) {
System.out.println( Math.abs(2)     ); // 2
System.out.println( Math.abs(-2)    ); // 2

System.out.println( Math.abs(2.54)  ); // 2.54
System.out.println( Math.abs(-2.54) ); // 2.54

System.out.println( Math.abs(0)     ); // 0
System.out.println( Math.abs(3 + 5) ); // 8
System.out.println( Math.abs(3 - 5) ); // 2
}
}``````

## 1. Documentation

 Syntax ``````package java.lang; public final class Math { public static int abs(int number) { ... } public static long abs(long number) { ... } public static float abs(float number) { ... } public static double abs(double number) { ... } }`````` Note: Classes in the `java.lang` package are imported automatically, so it is not necessary to do it manually - we use just `Math.abs()` call. Parameters `number` - `double`, `float`, `int`, or `long` value (primitive value). Result The absolute value calculated from the `number` (primitive value). Description `Math.abs()` is a static method that takes only one parameter and returns absolute number parameter value. The absolute value of the number x denoted |x|, is the non-negative value of x without regard to its sign.

2. Math.abs() custom implementation

``````public class CustomMath {

static double abs(double x) {
if (x < 0) {
return -x;
}
return x;
}

public static void main(String[] args) {
System.out.println( abs(2.0) ); // 2.0
System.out.println( abs(-2.0)); // 2.0
System.out.println( abs(0.0) ); // 0.0
}
}``````
Note: there are few ways to change sign to opposite if `(x < 0)` is `true`:
• `x = -x`
• `x *= -1`
• `x = ~x + 1`(not for double)

## References

1. Absolute value - wikipedia
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