Week 6: Methods of OO Programming/08. Comparable Point

In the program, the class 'Point', which you are familiar from the beginning of the tutorial, is defined.

Implement a 'comparison method' for the class:
public int compareTo(Point anotherPoint)

The comparison value of two points is based on the distance of the points from the origin - the greater the distance, the "larger" the point.
Note that the class already has a necessary method for calculating the distance.




import java.util.ArrayList;
import java.util.Collections;
import java.util.Random;

public class Test{
    public static void main(String[] args){
        final Random r = new Random();
        
        
        ArrayList<Point> points = new ArrayList<>();
        
        points.add(new Point(-4,-3));
        points.add(new Point(1,2));
        points.add(new Point(6,-3));
        points.add(new Point(-1,0));
        points.add(new Point(-14,1));
        points.add(new Point(1,11));
        points.add(new Point(-5,-5));
        points.add(new Point(-1,8));
        
        System.out.println("Points before:");
        points.stream().forEach(pt -> System.out.println("" + pt));
        
        Collections.sort(points);
        System.out.println("Points sorted:");
        points.stream().forEach(pt -> System.out.println(pt));

    }
}





class Point implements Comparable<Point>{
    private int x;
    private int y;
    
    public Point(int x, int y) {
        this.x = x;
        this.y = y;
    }

    public int getX() {
        return x;
    }

    public void setX(int x) {
        this.x = x;
    }

    public int getY() {
        return y;
    }

    public void setY(int y) {
        this.y = y;
    }


    //////////////////////////////////////////////
    // object method calls class method
    //////////////////////////////////////////////
    public double getDistance() {
        return Point.distanceFromOrigin(this);
    }
    
    public static double distanceFromOrigin(Point point) {
        return Math.sqrt(point.getX() * point.getX() + 
                point.getY() * point.getY());
    }
    
    @Override
    public String toString() {
        return "(" + x + "," + y + ") - distance: " + getDistance();
    }
    //////////////////////////////////////////////





    //ADD
    public int compareTo(Point anotherPoint) {
        double thisDistance = this.getDistance();
        double otherDistance = anotherPoint.getDistance();
    
        if (thisDistance < otherDistance) {
            return -1;
        } 
        else if (thisDistance > otherDistance) {
            return 1;
        } 
        else {
            return 0;
        }
    }

    

}






Points before:
(-4,-3) - distance: 5.0
(1,2) - distance: 2.23606797749979
(6,-3) - distance: 6.708203932499369
(-1,0) - distance: 1.0
(-14,1) - distance: 14.035668847618199
(1,11) - distance: 11.045361017187261
(-5,-5) - distance: 7.0710678118654755
(-1,8) - distance: 8.06225774829855

Points sorted:
(-1,0) - distance: 1.0
(1,2) - distance: 2.23606797749979
(-4,-3) - distance: 5.0
(6,-3) - distance: 6.708203932499369
(-5,-5) - distance: 7.0710678118654755
(-1,8) - distance: 8.06225774829855
(1,11) - distance: 11.045361017187261
(-14,1) - distance: 14.035668847618199