Double Dispatch Point, Java

Language: Layout:

//'main' method must be in a class 'Rextester'.
//Compiler version 1.8.0_111

import java.util.*;
import java.lang.*;

interface Point {
    Point convertTo(CoordinateSystem cs);
}

class CartesianPoint implements Point {
    CartesianPoint(double x, double y) {
        this.x = x;
        this.y = y;
    }

public Point convertTo(CoordinateSystem cs) {
        return cs.convert(this);
    }

double x;
    double y;
}

class PolarPoint implements Point {
    public PolarPoint(double angle, double radius) {
        this.angle = angle;
        this.radius = radius;
    }

public Point convertTo(CoordinateSystem cs) {
        return cs.convert(this);
    }

double angle;
    double radius;
}

interface CoordinateSystem {
    Point convert(CartesianPoint p);
    Point convert(PolarPoint p);

double distance(Point p1, Point p2);
}

class CartesianCoordinateSystem implements CoordinateSystem {
    public Point convert(CartesianPoint p) {
        return p;
    }

public Point convert(PolarPoint p) {
        double x = p.radius * Math.cos(p.angle);
        double y = p.radius * Math.sin(p.angle);
        return new CartesianPoint(x, y);
    }

public double distance(Point p1, Point p2) {
        CartesianPoint cp1 = (CartesianPoint)p1.convertTo(this);
        CartesianPoint cp2 = (CartesianPoint)p2.convertTo(this);

double a = cp1.x - cp2.x;
        double b = cp1.y - cp2.y;
        return Math.sqrt((a * a) + (b * b));
    }
}

class Rextester {
    public static void main(String[] args) {
        PolarPoint p1 = new PolarPoint(1.23, 5);
        CartesianPoint p2 = new CartesianPoint(4, 6);
        CartesianCoordinateSystem cs = new CartesianCoordinateSystem();
        
        CartesianPoint cp1 = (CartesianPoint)cs.convert(p1);
        System.out.println("P1=(" + cp1.x + "," + cp1.y + ")");
        System.out.println("P2=(" + p2.x + "," + p2.y + ")");
        System.out.println("DISTANCE=" + cs.distance(p1, p2));
    }
}

[ + ] Show input
Compilation time: 0.62 sec, absolute running time: 0.14 sec, cpu time: 0.08 sec, memory peak: 18 Mb, absolute service time: 0,77 sec