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Java - Math.log() method example

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Kara

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The Math.log() method returns the natural logarithm (base e) of a number.

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public class MathExample {
​
    public static void main(String[] args) {
        // Natural logarithm (logarithm with base e):
        //                            x            y
        System.out.println( Math.log( 1    ) ); // 0
        System.out.println( Math.log( 7    ) ); // 1.9459101490553132
        System.out.println( Math.log( 10   ) ); // 2.3025850929940460
        System.out.println( Math.log( 100  ) ); // 4.6051701859880920
        System.out.println( Math.log( 1000 ) ); // 6.9077552789821370
​
        System.out.println( Math.log( -1        ) ); //  NaN
        System.out.println( Math.log(  0        ) ); // -Infinity
        System.out.println( Math.log( Double.POSITIVE_INFINITY ) ); // +Infinity
​
        System.out.println( Math.E ); // 2.718281828459045
​
        // Logarithm with custom base is placed in below example.
    }
}

The Math.log() method is presented on the following chart:

Math.log(x) function visualization - Java Math Object.

1. Documentation

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Syntax	xxxxxxxxxx 1 package java.lang; 2 3 public final class Math { 4 5 public static double log(double x) { ... } 6 7 } Note: Classes in the `java.lang` package are imported automatically, so it is not necessary to do it manually - we use just `Math.log()` call.
Parameters	`x` - double value in the range `0` to `+Infinitive` (primitive value).
Result	`number` value calculated as ln(x) mathematical function (primitive value). If `x` is negative it returns `NaN`. If `x` is equal to `0` it returns `-Infinity`. If `x` is equal to `+Infinity` it returns `-Infinity`.
Description	`log` is a static method that takes one parameter and returns an approximation of the ln(x) function (natural logarithm function - logarithm with base `e`).

2. Logarithm with custom base example

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This example shows a logarithmic function calculation with its own base.

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public class MathExample {
    
    static double calculateLogarithm(double base, double x) {
        double a = Math.log(x);
        double b = Math.log(base);
​
        return a / b;
    }
​
    public static void main(String[] args) {
        // Logarithm with custom base:
        //                                    base      x               y
        System.out.println( calculateLogarithm( 2,      2      ) ); //  1.0
        System.out.println( calculateLogarithm( 2,      4      ) ); //  2.0
        System.out.println( calculateLogarithm( Math.E, Math.E ) ); //  1.0
        System.out.println( calculateLogarithm( 3,      9      ) ); //  2.0
        System.out.println( calculateLogarithm( 3,      81     ) ); //  4.0
        System.out.println( calculateLogarithm( 10,     10     ) ); //  1.0
    }
}