How do I get signum function of a number?

The code below show you how to get the signum function of a number using the Math.signum() static method call. This method extracts the sign of a real number. If you have a number of x the signum function of x is -1 if x < 0; 0 if x = 0 and 1 if x > 0.

package org.kodejava.example.math;

public class SignumExample {

    public static void main(String[] args) {
        Double zero = 0.0D;
        Double negative = -25.0D;
        Double positive = 15.0D;

        //
        // Get the signum function of value of a number.
        // It returns:
        // * 0 if the value is zero.
        // * 1.0 if value is greater than zero.
        // * -1.0 if value is less than zero.
        //
        double sign1 = Math.signum(zero);
        double sign2 = Math.signum(negative);
        double sign3 = Math.signum(positive);

        //
        // For floating-point value
        //
        float sign4 = Math.signum(zero.floatValue());
        float sign5 = Math.signum(negative.floatValue());
        float sign6 = Math.signum(positive.floatValue());

        System.out.println("In double:");
        System.out.println("Signum of " + zero + " is " + sign1);
        System.out.println("Signum of " + negative + " is " + sign2);
        System.out.println("Signum of " + positive + " is " + sign3);

        System.out.println("In float:");
        System.out.println("Signum of " + zero + " is " + sign4);
        System.out.println("Signum of " + negative + " is " + sign5);
        System.out.println("Signum of " + positive + " is " + sign6);
    }
}

Here is the output of the program:

In double:
Signum of 0.0 is 0.0
Signum of -25.0 is -1.0
Signum of 15.0 is 1.0
In float:
Signum of 0.0 is 0.0
Signum of -25.0 is -1.0
Signum of 15.0 is 1.0

How do I raised a number to the power of n?

The static method Math.pow(double a, double b) can be use to raised the value specified in the a to the power of the value specified in b.

package org.kodejava.example.math;

public class PowerExample {

    public static void main(String[] args) {
        double cubeRoot = 5d;

        //
        // Get the cubed number of cube root
        // x cubed = x^3 (multiplication three times)
        //
        double cubed = Math.pow(cubeRoot, 3);
        System.out.println(cubeRoot + " cubed is " + cubed);
    }
}

Our program print the following output:

5.0 cubed is 125.0

How do I calculate logarithm?

We can calculate logarithm using the Math.log10() and the Math.log() static method call.

package org.kodejava.example.math;

public class LogarithmExample {

    public static void main(String[] args) {
        double number1 = 1000.0d;
        double number2 = 999.0d;

        //
        // Get common logarithm
        //
        double log10 = Math.log10(number1);
        System.out.println("Common logarithm of " + number1 + " = " + log10);

        //
        // Get natural logarithm
        //
        double loge = Math.log(number1);
        System.out.println("Natural logarithm of " + number1 + " = " + loge);
    }
}

The output of the program is:

Common logarithm of 1000.0 = 3.0
Natural logarithm of 1000.0 = 6.907755278982137