qualcuno riesce a spiegarmi in modo semplice come funziona questa classe?

codice:
public class Whiteboard extends JPanel {
	private String wb_name;


	private Point start;
	private Point stop;
	private UserSession usersession;
	private Shape shape;
	private String stroke;
	private Path2D path = new Path2D.Double();


	public Whiteboard(String name, UserSession usersession) {
		wb_name = name;
		this.usersession = usersession;
		setBackground(Color.white);
		PathListener listener = new PathListener();
		addMouseListener(listener);
		addMouseMotionListener(listener);
		this.setVisible(true);
	}


	public void paintComponent(Graphics gc) {
		super.paintComponent(gc);


		Graphics2D g2 = (Graphics2D) gc;


		if (start != null && stop != null) {
			BasicStroke stroke = new BasicStroke(1);
			Shape strokedShape = stroke.createStrokedShape(shape);
			g2.draw(strokedShape);
			g2.fill(strokedShape);
		}
	}


	public String getName() {
		return wb_name;
	}


	public void setName(String name) {
		wb_name = name;
	}


	private class PathListener extends MouseAdapter {


		public void mousePressed(MouseEvent event) {
			start = event.getPoint();
			shape = path;
			
		}


		public void mouseDragged(MouseEvent event) {
			stop = event.getPoint();


			path = (Path2D) shape;
			path.moveTo(start.x, start.y);
			path.lineTo(stop.x, stop.y);
			shape = path;
			start = stop;
			
			repaint();
		}


		public void mouseReleased(MouseEvent event) {
			path = (Path2D) shape;
			try {
				path.closePath();
			} catch (Exception ingore) {
			}
			shape = path;
			


			repaint();


		}


	}


}