Java swing图形绘制并用颜色填充选定的矩形

/**
 * @Title:
 * @Description:TODO
 * @Company:HF
 * @ClassName:Exam.java   
 * @Author:wushigao
 * @CreateDate:2022年11月29日上午10:39:55 
 * @UpdateUser:wushigao
 * @UpdateDate:2022年11月29日 上午10:39:55 
 * @Version:1.0
 */
import java.awt.AlphaComposite;
import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Container;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.Rectangle;
import java.awt.Stroke;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionListener;
import java.util.ArrayList;

import javax.swing.JFrame;
import javax.swing.JPanel;
public class Exam extends JPanel implements MouseMotionListener {

    private static final int recW = 50;
    private static final int MAX = 100;
    private Rectangle[] rect = new Rectangle[MAX];
    private int numOfRecs = 0;
    private int currentSquareIndex = -1;
    private Point startPoint = new Point();
    private Point currentPoint = new Point();
    private int x, y, width, height;
    private Stroke dashedStroke = new BasicStroke(0.0f, BasicStroke.CAP_ROUND,
            BasicStroke.CAP_SQUARE, 5.0f, new float[] { 5f, 5f, 5f, 5f }, 5.0f);

    ArrayList list = new ArrayList();

    public Exam() {

        addRect(50, 50);
        addRect(100, 50);
        addRect(150, 50);
        addRect(200, 50);
        addRect(250, 50);
        addRect(300, 50);
        addRect(350, 50);
        addRect(400, 50);
        addRect(450, 50);
        addRect(500, 50);
        //
        addRect(50, 100);
        addRect(100, 100);
        addRect(150, 100);
        addRect(200, 100);
        addRect(250, 100);
        addRect(300, 100);
        addRect(350, 100);
        addRect(400, 100);
        addRect(450, 100);
        addRect(500, 100);
        //
        addRect(50, 150);
        addRect(100, 150);
        addRect(150, 150);
        addRect(200, 150);
        addRect(250, 150);
        addRect(300, 150);
        addRect(350, 150);
        addRect(400, 150);
        addRect(450, 150);
        addRect(500, 150);
        //
        addRect(50, 200);
        addRect(100, 200);
        addRect(150, 200);
        addRect(200, 200);
        addRect(250, 200);
        addRect(300, 200);
        addRect(350, 200);
        addRect(400, 200);
        addRect(450, 200);
        addRect(500, 200);

        addMouseListener(new MouseAdapter() {

            @Override
            public void mousePressed(MouseEvent evt) {
                startPoint = evt.getPoint();
            }

            public void mouseReleased(MouseEvent e) {

                System.out.println(" mouseReleased is" + e.getX() +" y i s"
                        + e.getY());
                Graphics g = getGraphics();
                Graphics2D g2 = (Graphics2D) g;
                g2.setComposite(AlphaComposite.SrcOver.derive(0.8f));
                Color myColour = new Color(255, 0, 0);
                g.setColor(myColour);
                x = Math.min(startPoint.x, currentPoint.x);
                y = Math.min(startPoint.y, currentPoint.y);
                width = Math.abs(startPoint.x - currentPoint.x);
                height = Math.abs(startPoint.y - currentPoint.y);
                rect[numOfRecs] = new Rectangle(x, y, width, height);
                // System.out.println("list size is:"+list.size());
                 Rectangle ggg=new Rectangle(x, y, width, height);
            for(Rectangle rect3d: rect){
                if(ggg.intersects(rect3d)){
                g2.fill(rect3d);
                }
                else
                    System.out.println("doesn't contains");
                }
repaint();
            }

        });

        addMouseMotionListener(this);
    }

    @Override
    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        for (int i = 0; i < numOfRecs; i++) {
            ((Graphics2D) g).draw(rect[i]);
            list.add(rect[i]);
        }

        x = Math.min(startPoint.x, currentPoint.x);
        y = Math.min(startPoint.y, currentPoint.y);
        width = Math.abs(startPoint.x - currentPoint.x);
        height = Math.abs(startPoint.y - currentPoint.y);
        ((Graphics2D) g).setStroke(dashedStroke);
        g.setColor(Color.BLACK);
        g.drawRect(x, y, width, height);
        // Rectangle dashedRec=new Rectangle(x, y, width, height);

    }

    public void addRect(int x, int y) {
        if (numOfRecs < MAX) {
            rect[numOfRecs] = new Rectangle(x, y, recW, recW);
            currentSquareIndex = numOfRecs;
            numOfRecs++;
            repaint();
        }
    }

    @Override
    public void mouseMoved(MouseEvent event) {
    }

    @Override
    public void mouseDragged(MouseEvent event) {

        currentPoint = event.getPoint();
        repaint();
    }

    public static void main(String[] args) {
        JFrame jFrame = new JFrame();
        jFrame.setTitle("");
        jFrame.setSize(600, 300);
        Container cPane = jFrame.getContentPane();
        cPane.add(new Exam());
        jFrame.setVisible(true);
    }
}