// relocate only works on defualt monitor
	public void relocate(JFrame f){
		/*If this function is called, it will relocate
		 the window to a new random position on the screen
		 */
		Random r = new Random();
		// Find Screen size
		Toolkit tk = Toolkit.getDefaultToolkit();
		Dimension d = tk.getScreenSize();
		// use the Dimension find and reset width and height
		int x = r.nextInt(d.width - getWidth());
		int y = r.nextInt(d.height - getHeight());
		f.setLocation(x,y);
	};

JFrame Relocate

Java