Coordinate.java

public void paint(Graphics g) {
    g.setColor(0x0000ff);
    g.rotate(
        (float)(Math.PI/4.0),
        getAbsoluteX()+getWidth()/2,
        getAbsoluteY()+getHeight()/2
    );
    g.drawRect(getX() + 5, getY() + 5, getWidth() - 10, getHeight() - 10);
    g.rotate(
        -(float)(Math.PI/4.0),
        getAbsoluteX()+getWidth()/2,
        getAbsoluteY()+getHeight()/2
    );
}