/* * Copyright (c) 2000 David Flanagan.  All rights reserved. * This code is from the book Java Examples in a Nutshell, 2nd Edition. * It is provided AS-IS, WITHOUT ANY WARRANTY either expressed or implied. * You may study, use, and modify it for any non-commercial purpose. * You may distribute it non-commercially as long as you retain this notice. * For a commercial use license, or to purchase the book (recommended), * visit http://www.davidflanagan.com/javaexamples2. */package com.davidflanagan.examples.classes;/** * This class represents complex numbers, and defines methods for performing * arithmetic on complex numbers. **/public class ComplexNumber {    // These are the instance variables.  Each ComplexNumber object holds    // two double values, known as x and y.  They are private, so they are    // not accessible from outside this class.  Instead, they are available     // through the real() and imaginary() methods below.    private double x, y;    /** This is the constructor.  It initializes the x and y variables */    public ComplexNumber(double real, double imaginary) {        this.x = real;        this.y = imaginary;    }    /**      * An accessor method.  Returns the real part of the complex number.     * Note that there is no setReal() method to set the real part.  This means     * that the ComplexNumber class is "immutable".     **/    public double real() { return x; }        /** An accessor method. Returns the imaginary part of the complex number */    public double imaginary() { return y; }        /** Compute the magnitude of a complex number */    public double magnitude() { return Math.sqrt(x*x + y*y); }    /**      * This method converts a ComplexNumber to a string.  This is a method of     * Object that we override so that complex numbers can be meaningfully     * converted to strings, and so they can conveniently be printed out with     * System.out.println() and related methods     **/    public String toString() { return "{" + x + "," + y + "}"; }        /**      * This is a static class method.  It takes two complex numbers, adds     * them, and returns the result as a third number.  Because it is static,     * there is no "current instance" or "this" object.  Use it like this:     * ComplexNumber c = ComplexNumber.add(a, b);     **/    public static ComplexNumber add(ComplexNumber a, ComplexNumber b) {        return new ComplexNumber(a.x + b.x, a.y + b.y);    }    /**     * This is a non-static instance method by the same name.  It adds the     * specified complex number to the current complex number.  Use it like     * this:     * ComplexNumber c = a.add(b);     **/    public ComplexNumber add(ComplexNumber a) {        return new ComplexNumber(this.x + a.x, this.y+a.y);    }    /** A static class method to multiply complex numbers */    public static ComplexNumber multiply(ComplexNumber a, ComplexNumber b) {        return new ComplexNumber(a.x*b.x - a.y*b.y, a.x*b.y + a.y*b.x);    }    /** An instance method to multiply complex numbers */    public ComplexNumber multiply(ComplexNumber a) {        return new ComplexNumber(x*a.x - y*a.y, x*a.y + y*a.x);    }}