public class CustomListener implements MouseListener {

    private Field field;

    public CustomListener(Field field) {
        this.field = field;
    }

    @Override
    public void mouseClicked(MouseEvent e) {
        int x = e.getX();
        if(x <= 500) {
            System.out.println(x);
            field.img = field.img_c;
            field.repaint();
        }
    }

    @Override
    public void mousePressed(MouseEvent e) {

    }

    @Override
    public void mouseReleased(MouseEvent e) {

    }

    @Override
    public void mouseEntered(MouseEvent e) {

    }

    @Override
    public void mouseExited(MouseEvent e) {

    }
}