用JAVA做画图版程序，可以画直线

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

public class Drawline extends JFrame {
private Draw dr;

private JButton b1;

private Color cc;

public Drawline() {
b1 = new JButton("change");
b1.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
cc = JColorChooser.showDialog(Drawline.this, "please a color",
cc);
dr.setColor(cc);
}
});
dr = new Draw();
dr.setBackground(Color.white);
Container c = getContentPane();
c.setLayout(new FlowLayout());
c.add(dr);
c.add(b1);
setSize(600, 500);
show();
}

public static void main(String args[]) {
Drawline dl = new Drawline();
dl.addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent e) {
System.exit