用Java设计一个简单的画图程序，即使用鼠标绘图。该应用程序窗体标题为“Drag to draw”

以下是使用Java Swing实现的简单画图程序示例：

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class Main {
    public static void main(String[] args) {
        JFrame frame = new JFrame("Drag to draw");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        JPanel panel = new JPanel() {
            private Point startPoint = null;
            private Point endPoint = null;

            @Override
            public void paintComponent(Graphics g) {
                super.paintComponent(g);
                if (startPoint != null && endPoint != null) {
                    g.drawLine(startPoint.x, startPoint.y, endPoint.x, endPoint.y);
                }
            }

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

            @Override
            public void mouseDragged(MouseEvent e) {
                endPoint = e.getPoint();
                repaint();
            }

            @Override
            public void mouseReleased(MouseEvent e) {
                endPoint = e.getPoint();
                repaint();
                startPoint = null;
                endPoint = null;
            }
        };

        panel.setPreferredSize(new Dimension(400, 400));

        frame.getContentPane().add(panel);
        frame.pack();
        frame.setVisible(true);
    }
}

运行该程序，在窗口中按下鼠标左键并拖动，可以绘制直线。松开鼠标左键后，绘制停止。