Screen Tearing - GameKernel.java

GameKernel.java

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.Timer;


public class GameKernel implements Runnable {

    public static int playerX = 400;
    public static int playerY = 300;
    private int moveVel = 10;
    private int direction = 1;

    private Timer timer;
    public static final int TIMESTEP_MS = 10;
    
    public void run() {
        final GameWindow gw = new GameWindow();

        ActionListener taskPerformer = new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                update();
                gw.render();
            }
            
        };
        timer = new Timer(TIMESTEP_MS, taskPerformer);
        timer.start();
    }

    public void update() {
        playerX += direction * moveVel;
        if (playerX >= GameWindow.SIZE.width - 100) {
            direction *= -1;
        }
        else if (playerX <= 100) {
            direction *= -1;
        }
    }

}