Keys

public class BasicKeys  {

    private boolean[] keys = new boolean[4];
    private int double x,y;

    public static void main(String args[]) {

        JFrame f = new JFrame("Basic keys");
        f.setResizable(false);
        f.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);

        f.add(new Keys());

        f.pack();

        f.setVisible(true);
        f.setLocationRelativeTo(null);
    }

}

public class Keys extends JPanel implements ActionListener{

    public Keys()
    {
        setPreferredSize(new Dimension(500, 500));
        setFocusable(true);
        addKeyListener(new KeyController());

    }

    @Override
    public void paintComponent(Graphics g) {
        super.requestFocus();
        super.paintComponent(g);
        Graphics2D g2d = (Graphics2D)g;

        g2d.fillrect(this.x, this.y, 40, 40);

        Thread.sleep(10);

        g2d.dispose();
        repaint();
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        repaint();
    }


        private class KeyController extends KeyAdapter {


        private double dx, dy;


        public KeyController()
        {
            for(int i= 0; i < 4; i++)
            {
                keys[i] = false;
            }
        }


        @Override
        public void keyPressed(KeyEvent e) {
            switch(e.getKeyCode())
            {
                case KeyEvent.VK_RIGHT:
                    dx = 2;
                    if(keys[2])
                        dy = -2;
                    else if(keys[3])
                            dy = 2;
                    keys[0] = true;
                break;
                case KeyEvent.VK_LEFT:
                    dx = -2;
                    if(keys[2])
                       dy = -2;
                    else if(keys[3])
                       dy = 2;

                    keys[1] = true;
                break;
                case KeyEvent.VK_UP:
                    dy = -2;
                    if(keys[0])
                        dx = 2;
                    else if(keys[1])
                        dx = -2;
                    keys[2] = true;
                break;
                case KeyEvent.VK_DOWN:
                    dy = 2;
                    if(keys[0])
                        dx = 2;
                    else if(keys[1])
                        dx = -2;
                    keys[3] = true;
                break;
                case KeyEvent.VK_ESCAPE:
                    showMenu();
                break;
            }


            sqr.setDx(dx);
            sqr.setDy(dy);

        }

        @Override
        public void keyReleased(KeyEvent e){

            if((e.getKeyCode() ==  KeyEvent.VK_LEFT))
            {
               keys[1] = false;
               this.dx = 0;
            }
            else if((e.getKeyCode() == KeyEvent.VK_RIGHT))
            {
               keys[0] = false;
               this.dx = 0;
            }
            else if((e.getKeyCode() == KeyEvent.VK_UP))
            {
                keys[2] = false;
                this.dy = 0;
            }
            else if((e.getKeyCode() ==  KeyEvent.VK_DOWN))
            {
                keys[3] = false;
                this.dy = 0;
            }

            sqr.setDx(this.dx);
            sqr.setDy(this.dy);

        }


    }

}