Override container 后无法 setColor, 原来覆盖的是 print 方法但应该是 paint 方法

public class Yard extends Frame {

	public static final int ROWS = 30;
	public static final int COLS = 30;
	public static final int BLOCK_SIZE = 15;

	
	public void launch() {
		this.setLocation(200, 200);
		this.setSize(COLS * BLOCK_SIZE, ROWS * BLOCK_SIZE);
		this.addWindowListener(new WindowAdapter() {

			@Override
			public void windowClosing(WindowEvent e) {
				System.exit(0);
			}
			
		});
		this.setVisible(true);
	}
	
	public static void main(String[] args) {
		new Yard().launch();
	}
	
	@Override
	public void paint(Graphics g) {
		Color c = g.getColor();
		g.setColor(Color.GRAY);
		g.fillRect(0, 0, COLS * BLOCK_SIZE, ROWS * BLOCK_SIZE);

		
		g.setColor(c);
		

	}

}
Override container后无法setColo