ComplexNumber.java | An implementation of Complex Numbers

package plane.complex;

/**
 * <code>ComplexNumber</code> is a class which implements complex numbers in Java.
 * It includes basic operations that can be performed on complex numbers such as,
 * addition, subtraction, multiplication, conjugate, modulus and squaring.
 *
 * @author      Abdul Fatir
 * @version     1.0
 *
 */
public class ComplexNumber
{
    /**
    * The real, Re(z), part of the <code>ComplexNumber</code>.
    */
    private double real;
    /**
    * The imaginary, Im(z), part of the <code>ComplexNumber</code>.
    */
    private double imaginary;
    /**
    * Constructs a new <code>ComplexNumber</code> object with both real and imaginary parts 0 (z = 0 + 0i).
    */

    public ComplexNumber()
    {
        real = 0.0;
        imaginary = 0.0;
    }

    /**
    * Constructs a new <code>ComplexNumber</code> object.
    * @param real the real part, Re(z), of the complex number
    * @param imaginary the imaginary part, Im(z), of the complex number
    */

    public ComplexNumber(double real, double imaginary)
    {
        this.real = real;
        this.imaginary = imaginary;
    }

    /**
    * Adds another <code>ComplexNumber</code> to the current complex number.
    * @param complex_number the complex number to be added to the current complex number
    */

    public void add(ComplexNumber complex_number)
    {
        this.real = this.real + complex_number.real;
        this.imaginary = this.imaginary + complex_number.imaginary;
    }

    /**
    * The complex conjugate of the current complex number.
    * @return a <code>ComplexNumber</code> object which is the conjugate of the current complex number
    */

    public ComplexNumber conjugate()
    {
        return new ComplexNumber(this.real,-this.imaginary);
    }

    /**
    * The modulus, magnitude or the absolute value of current complex number.
    * @return the magnitude or modulus of current complex number
    */

    public double mod()
    {
        return Math.sqrt(Math.pow(this.real,2) + Math.pow(this.imaginary,2));
    }

    /**
    * The square of the current complex number.
    * @return a <code>ComplexNumber</code> object which is the square of the current complex number
    */

    public ComplexNumber square()
    {
        double _real = this.real*this.real - this.imaginary*this.imaginary;
        double _imaginary = 2*this.real*this.imaginary;
        return new ComplexNumber(_real,_imaginary);
    }

    /**
    * Multiplies another <code>ComplexNumber</code> to the current complex number.
    * @param complex_number the complex number to be multiplied to the current complex number
    */

    public void multiply(ComplexNumber complex_number)
    {
        double _real = this.real*complex_number.real - this.imaginary*complex_number.imaginary;
        double _imaginary = this.real*complex_number.imaginary + this.imaginary*complex_number.real;

        this.real = _real;
        this.imaginary = _imaginary;
    }

    /**
    * Prints the complex number in x + yi format
    */

    public void print()
    {
        System.out.println(this.real+" + "+this.imaginary+"i");
    }
}