int px = 100, py = 380;          // player position
    int pw = 34, ph = 44;            // player size
    int speed = 5;
    boolean leftHeld, rightHeld;

    void update() {
        if (leftHeld)  px -= speed;
        if (rightHeld) px += speed;
    }

    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        g.setColor(new Color(255, 119, 0));
        g.fillRect(px, py, pw, ph);
    }

    public void keyPressed(KeyEvent e) {
        if (e.getKeyCode() == KeyEvent.VK_LEFT)  leftHeld = true;
        if (e.getKeyCode() == KeyEvent.VK_RIGHT) rightHeld = true;
    }
    public void keyReleased(KeyEvent e) {
        if (e.getKeyCode() == KeyEvent.VK_LEFT)  leftHeld = false;
        if (e.getKeyCode() == KeyEvent.VK_RIGHT) rightHeld = false;
    }
    public void keyTyped(KeyEvent e) {}