First Class

import java.awt.*;
import javax.swing.JFrame;

public class MovingSquaresApplication extends JFrame implements Runnable {

    private static final Dimension WindowSize = new Dimension(600,600);
    private static final int NUMGAMEOBJECTS = 30;
    private  GameObject[] GameObjectsArray  = new GameObject[NUMGAMEOBJECTS];



    public MovingSquaresApplication(){
        //Create and set up the window.
        this.setTitle("Moving Squares");
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        //Display the window, centred on the screen
        Dimension screensize = java.awt.Toolkit.getDefaultToolkit().getScreenSize();
        int x = screensize.width/2 - WindowSize.width/2;
        int y = screensize.height/2 - WindowSize.height/2;
        setBounds(x, y, WindowSize.width, WindowSize.height);
        setVisible(true);

        for (int i = 0; i < NUMGAMEOBJECTS; i++){
            GameObjectsArray[i] = new GameObject();

        }


        Thread t = new Thread(this);
        t.start();




    }

    public static void main(String[] args){

        MovingSquaresApplication app = new MovingSquaresApplication();

    }


    public void run(){
        while(true){

        try {
            for (int a = 0; a < NUMGAMEOBJECTS; a++){
                GameObjectsArray[a].move();
                }

            Thread.sleep(16);
        } catch (InterruptedException e) {

        }
        this.repaint();
                }


    }

    public void paint(Graphics g){
        g.clearRect(0, 0, 600, 600);

        for(int z = 0; z < NUMGAMEOBJECTS; z++){
            GameObjectsArray[z].paint(g);

        }

    }

}