java 怎麼畫一個空心的框

	public static void main(String[] args) {
		JFrame j = new JFrame();
		JPanel p =new JPanel();
		j.setSize(600, 400);
		j.setUndecorated(true);
		j.setLocationRelativeTo(null);
		/**
		 * 設置背景透明
		 */
		j.setBackground(new Color(0,0,0,0));
		j.setVisible(true);
		/**
		 * 添加border
		 */
		j.add(p);
		p.setBackground(new Color(0,0,0,0));
		p.setBorder(new LineBorder(new Color(255, 0, 0)));
	}