programming-examples/java/Data_Structures/Complex.java

public class Complex {
	final double x;
	final double y;

	public Complex(double x) {
		this.x = x;
		this.y = 0;
	}

	public Complex(double x, double y) {
		this.x = x;
		this.y = y;
	}

	public Complex conj() {
		return new Complex(x, -y);
	}

	public Complex sub(Complex b) {
		return new Complex(x - b.x, y - b.y);
	}

	public Complex add(Complex b) {
		return new Complex(x + b.x, y + b.y);
	}

	public Complex mul(Complex b) {
		return new Complex(x * b.x - y * b.y, x * b.y + y * b.x);
	}

	public Complex div(Complex b) {
		return this.mul(b.conj()).mul(1 / b.len2());
	}

	public Complex mul(double b) {
		return new Complex(x * b, y * b);
	}

	public double len2() {
		return x * x + y * y;
	}

	public double abs() {
		return Math.sqrt(x * x + y * y);
	}

	public Complex norm() {
		return abs() == 0 ? new Complex(0, 0) : mul(1 / abs());
	}

	public double cross(Complex b) {
		return x * b.y - y * b.x;
	}

	double cross2(Complex b) {
		return this.conj().mul(b).y;
	}

	public double dot(Complex b) {
		return x * b.x + y * b.y;
	}

	double dot2(Complex b) {
		return this.conj().mul(b).x;
	}

	public static Complex polar(double r, double theta) {
		return new Complex(r * Math.cos(theta), r * Math.sin(theta));
	}

	public static Complex exp(Complex a) {
		return polar(Math.exp(a.x), a.y);
	}

	public double arg() {
		return Math.atan2(y, x);
	}

	public Complex rot90() {
		return new Complex(-y, x);
	}

	public Complex rotate(Complex p, double angle) {
		return p.sub(this).mul(exp(new Complex(0, angle))).add(this);
	}

	public Complex rotate2(Complex p, double angle) {
		p = p.sub(this);
		double cs = Math.cos(angle);
		double sn = Math.sin(angle);
		return new Complex(p.x * cs - p.y * sn, p.x * sn + p.y * cs).add(this);
	}

	public Complex reflect(Complex p, Complex q) {
		Complex s = q.sub(p);
		return this.sub(p).div(s).conj().mul(s).add(p);
	}

	public double proj(Complex p) {
		return dot(p) / this.abs();
	}

	public static double angle(Complex a, Complex p, Complex b) {
		a = a.sub(p);
		b = b.sub(p);
		return Math.atan2(a.cross(b), a.dot(b));
	}

	@Override
	public String toString() {
		return "Complex [x=" + x + ", y=" + y + "]";
	}

	// Usage example
	public static void main(String[] args) {
		Complex z = new Complex(3, 2);
		z = z.div(z);
		System.out.println(z);
		System.out.println();

		Complex u = new Complex(0, 0);
		Complex v = new Complex(1, 0);
		Complex a = u.rotate(v, Math.PI * 1.0);
		Complex b = v.rot90().rot90();
		System.out.println(a);
		System.out.println(b);
	}
}