Примитивный графический редактор

import java.awt.event.*;
import java.awt.*;
import java.awt.geom.*;
import java.util.*;
import javax.swing.*;
 
public class MainClass {
    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                LinesFrame frame = new LinesFrame();
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setVisible(true);
            }
        });
    }
}
 
class LinesFrame extends JFrame
{
    public LinesFrame()
    {
        setTitle("Painting lines");
        setSize(DEFAULT_WIDTH, DEFAULT_HEIGHT);
 
        LinesComponent component = new LinesComponent();
        add(component);
    }
 
    public static final int DEFAULT_WIDTH = 400;
    public static final int DEFAULT_HEIGHT = 300;
}
 
class LinesComponent extends JComponent {
    public LinesComponent()
    {
        lines = new ArrayList<Line2D>();
        current = null;
        MouseHandler MH = new MouseHandler();
        addMouseListener(MH);
        addMouseMotionListener(MH);
    }
 
    public void paintComponent(Graphics g)
    {
        Graphics2D g2 = (Graphics2D) g;
        g2.setColor(Color.RED);
        for (Line2D line : lines)
            g2.draw(line);
    }
    ArrayList<Line2D> lines;
    Line2D current;
    Point2D begin;
    Point2D end;
    public void add(Point2D p1, Point2D p2)
    {
        current = new Line2D.Double(p1, p2);
        lines.add(current);
        repaint();
    }
    private class MouseHandler implements MouseMotionListener, MouseListener
    {
        public void mousePressed(MouseEvent event) {
            begin = event.getPoint();
 
 
        }
        public void mouseReleased(MouseEvent event) {
            end = event.getPoint();
            add(begin, end);
        }
 
        public void mouseDragged(MouseEvent event) {
            Graphics g = getGraphics();
            int x = event.getX();
            int y = event.getY();
            g.setColor(Color.RED);
            g.drawLine((int) begin.getX(), (int) begin.getY(), x, y);
        }
 
        @Override
        public void mouseMoved(MouseEvent mouseEvent) { }
        @Override
        public void mouseEntered(MouseEvent mouseEvent) {}
        @Override
        public void mouseExited(MouseEvent mouseEvent) { }
        @Override
        public void mouseClicked(MouseEvent mouseEvent) { }
 
    }
}

class LinesComponent extends JComponent {
    public LinesComponent()
    {
        lines = new ArrayList<Line2D>();
        current = null;
        addMouseListener(new MouseHandler());
        addMouseMotionListener(new MouseMotionHandler());
    }
 
    public void paintComponent(Graphics g)
    {
        Graphics2D g2 = (Graphics2D) g;
        g2.setColor(Color.RED);
        for (Line2D line : lines)
            g2.draw(line);
    }
    ArrayList<Line2D> lines;
    Line2D current;
    Point2D begin;
    Point2D end;
    
    
    private class MouseHandler extends MouseAdapter{
        public void mousePressed(MouseEvent event){
            begin = event.getPoint();
            current = new Line2D.Double(begin,begin);
            lines.add(current);
        }
    }
    
    
    private class MouseMotionHandler extends MouseMotionAdapter{
        public void mouseDragged(MouseEvent event) {
           end = event.getPoint();
            current.setLine(begin, end);
            repaint();
        }
    }
    
}

current = new Line2D.Double(begin,begin);