Complex Numbers

/*
 * Lu Liu
 * CSC-112 Intermediate Java Programming
 * FEB 15 2016
 * lliu0001@ student.stcc.edu
 *
 * Implementing Complex Numbers
 * define two doubles, known as the real part and the imaginary part.
 * define 4 constructors
 * define public methods
 */
package chapter09;

public class Complex {

    // define two doubles, known as the real part and the imaginary part.
    private double real;
    private double imag;

    // define 4 constructors
    public Complex(double real, double imag) {
        this.real = real;
        this.imag = imag;
    }

    public Complex(double real) {
        this.real = real;
        this.imag = 0;
    }

    public Complex() {
        this(0, 0);
    }

    // the constructor takes a String
    public Complex(String str) {
        String newStr = str.trim();
        char[] chars = newStr.toCharArray();
        if (newStr.indexOf("i") == -1)
            this.real = Double.parseDouble(newStr);
        else if (chars.length == 1) {
            this.imag = 1.0;
        } else if (chars.length == 2) {
            this.imag = (double) (chars[0] - '0');
        } else if (chars.length == 3) {
            if (Character.isDigit(chars[0])) {
                this.real = (double) (chars[0] - '0');
                this.imag = (chars[1] == '-') ? -1.0 : 1.0;
            } else
                this.imag = -(double) (chars[1] - '0');
        } else if (chars.length == 4) {
            if (Character.isDigit(chars[0])) {
                this.real = (double) (chars[0] - '0');
                this.imag = (chars[1] == '-') ? -(double) (chars[2] - '0') : (double) (chars[2] - '0');
            } else {
                this.real = -(double) (chars[1] - '0');
                this.imag = (chars[2] == '-') ? -1.0 : 1.0;
            }
        } else if (chars.length == 5) {
            this.real = -(double) (chars[1] - '0');
            this.imag = (chars[2] == '-') ? -(double) (chars[3] - '0') : (double)(chars[3] - '0');
        }
    }

    // define public methods
    public double getReal() {
        return real;
    }

    public double getImag() {
        return imag;
    }

    public Complex add(Complex c) {
        return new Complex((this.real + c.getReal()), (this.imag + c.getImag()));
    }

    public Complex subtract(Complex c) {
        return new Complex((this.real - c.getReal()), (this.imag - c.getImag()));
    }

    public Complex multiply(Complex c) {
        return new Complex((this.real * c.getReal() - this.imag * c.getImag()),
                (this.real * c.getImag() + c.getImag() * c.getImag()));
    }

    public Complex divide(Complex c) {
        double a = this.real;
        double b = this.imag;
        double x = c.getReal();
        double y = c.getImag();
        return new Complex((a * x + b * y) / (x * x + y * y), (b * x - a * y) / (x * x + y * y));
    }

    public double abs() {
        double a = this.getReal();
        double b = this.getImag();
        return Math.sqrt(a * a + b * b);
    }

    public Complex negate() {
        double a = this.getReal();
        double b = this.getImag();
        return new Complex(-a, -b);
    }

    public Complex conjugate() {
        return new Complex(this.getReal(), -this.getImag());
    }

    public double distance(Complex c) {
        double x = this.getReal() - c.getReal();
        double y = this.getImag() - c.getImag();
        return x * x + y * y;
    }

    public boolean equals(Complex c) {
        double minus = (this.abs() > c.abs()) ? (this.abs() - c.abs()) : -(this.abs() - c.abs());
        if (minus / this.abs() < 1E-6)
            return true;
        return false;
    }

    public boolean greaterThan(Complex c) {
        return (this.abs() > c.abs()) ? true : false;
    }

    public boolean lessThan(Complex c) {
        return !this.greaterThan(c);
    }

    public String toString() {
        if (this.getImag() > 0)
            return this.getReal() + "+" + (this.getImag() + "i");
        else if (this.getImag() == 0)
            return this.getReal() + "";
        else
            return this.getReal() + "" + (this.getImag() + "i");
    }
}