Kvadratiki

package kvadratiki;
import java.awt.*;
import java.awt.event.*;
import java.util.*;
import java.awt.geom.*;
import javax.swing.*;

public class Kvadratiki {
    public static void main(String[] args)
    {
        MouseFrame frame = new MouseFrame();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }
}
    class MouseFrame extends JFrame
    {
        public MouseFrame(){

        }
        {
            setTitle("Квадратики");
            setSize(500, 500);
            MousePanel panel = new MousePanel();
            add(panel);
        }
        //
        //
    }
    class MousePanel extends JPanel
    {
        public MousePanel()
        {
            squares = new ArrayList <Rectangle2D>();
            current = null;

            addMouseListener(new MouseHandler());
            addMouseMotionListener(new MouseMotionHandler());
        }
        public void paintComponent(Graphics g)
        {
            super.paintComponent(g);
            Graphics2D g2 = (Graphics2D) g;
            for (Rectangle2D r : squares)
            {
                g2.draw(r);
                }
            }


            public Rectangle2D find(Point2D p)
            {
                for (Rectangle2D r : squares)
                {
                    if (r.contains(p)) return r;
                }
                return null;
            }


            public void add(Point2D p)
            {
                double x = p.getX();
                double y = p.getY();

                current = new Rectangle2D.Double(
                        x - SIDELENGTH / 2,
                        y - SIDELENGTH / 2,
                        SIDELENGTH,
                        SIDELENGTH);
                squares.add(current);
                repaint();
            }


            public void remove(Rectangle2D s)
            {
                if (s==null) return;
                if (s == current) current = null;
                repaint();
            }

            private static final int SIDELENGTH = 10;
            private ArrayList<Rectangle2D> squares;
            private Rectangle2D current;
            private class MouseHandler extends MouseAdapter
            {
                public void mousePressed(MouseEvent event) {
                    current = find(event.getPoint());
                            if (current == null)
                                add(event.getPoint());
                            }
                public void mouseClicked(MouseEvent event)
                {
                    current = find(event.getPoint());
                    if (current != null && event.getClickCount() >= 2)
                        remove (current);
                }

            }

            private class MouseMotionHandler
                implements MouseMotionListener
                {
                public void mouseMoved(MouseEvent event)
                {
                    if (find(event.getPoint()) == null) {
                        setCursor(Cursor.getDefaultCursor());
                    for (Rectangle2D s: squares) {
                        int x = (int) s.getCenterX(), y = (int) s.getCenterY();
                        s.setFrame(x - SIDELENGTH / 2, y - SIDELENGTH / 2, SIDELENGTH ,SIDELENGTH);
                    }
                    repaint();
                    }
                    else {
                        setCursor(Cursor.getPredefinedCursor(Cursor.CROSSHAIR_CURSOR));
                        int x = (int) find(event.getPoint()).getCenterX(), y = (int) find(event.getPoint()).getCenterY();
                        find(event.getPoint()).setFrame (x - SIDELENGTH, y - SIDELENGTH, SIDELENGTH*2, SIDELENGTH*2 );
                        repaint();
                    }
                }

                public void mouseDragged(MouseEvent event)
                {
                    if (current == null)
                        return;

                        int x = event.getX();
                        int y = event.getY();

                        current.setFrame(
                                x - SIDELENGTH / 2,
                                y - SIDELENGTH / 2,
                                SIDELENGTH,
                                SIDELENGTH);
                        repaint();

                }
        }
    }