Pong - Game

Ball.java

package pong;

import processing.core.PGraphics;
import processing.core.PVector;

public class Ball {
    private PVector pos;
    private PVector vel;
    private int mag;

    public Ball(PVector pos, int mag) {
        this.pos = pos;
        this.mag = mag;
        this.vel = new PVector((float)Math.random()*18, (float)Math.random()*18);
    }

    public boolean checkCollision(int w, int h) {
        if (pos.y -mag< 0) {
            vel.y = -vel.y;
            pos.y = mag;
            return true;
        }

        if (pos.y+ mag >= h) {
            vel.y = -vel.y;
            pos.y = h-mag;
            return true;
        }

        if (pos.x -mag< 0) {
            vel.x = -vel.x;
            pos.x = mag;
            return true;
        }

        if (pos.x + mag >= w) {
            vel.x = -vel.x;
            pos.x = w -mag;
            return true;
        }
        return false;
    }

    public void draw(PGraphics gfx) {
        gfx.circle(pos.x, pos.y,mag);
    }

    public void move() {
        pos = PVector.add(pos,vel);
    }
}

Pong.java

package pong;

import processing.core.PApplet;
import processing.core.PVector;

import java.util.Vector;

public class Pong extends PApplet {
    //private Ball ball;
    private int collisions;
    private Vector<Ball> balls;

    public Pong() {
        collisions = 0;
        balls = new Vector<>();
    }

    @Override
    public void settings() {
        size(800,600);
    }

    @Override
    public void setup() {
        //ball = new Ball(new PVector(width/2,height/2),10);
        balls.add(new Ball(new PVector(width/2,height/2),10));
    }

    @Override
    public void draw() {
        background(55,55,55);
        for(var i = 0; i < balls.size();i++) {
            var ball = balls.get(i);
            ball.move();
            var collided = ball.checkCollision(width, height);
            if (collided) {
                collisions++;
                balls.add(new Ball(new PVector(width/2,height/2),10));
            }
            ball.draw(getGraphics());
        }
        textSize(48);
        text(collisions,width-200,40);
    }

    public static void main(String[] args) {
        PApplet.main("pong.Pong");
    }
}