java第一次上机实验--验证码

 package javashiyan;

 import java.awt.Color;
 import java.awt.event.ActionEvent;
 import java.awt.event.ActionListener;

 import javax.swing.*;

 public  class Yanzhen extends JFrame
 {
     //定义成员变量
     private Mypanel mp;
     private JButton b;
     private JTextField txt;
     private ActionListener listener;

     public Yanzhen()
     {
         Realize();
     }
     public void Realize()
     {
         JFrame f=new JFrame("验证码");
         //实例化
         b=new JButton();
         b.addActionListener(listener);
         ActionEvent e;
         b.setIcon(new ImageIcon("D://button//刷新.jpg"));//载入图片
         b.setLocation(200,100);//设置位置
         b.setSize(32,32);//设置大小
         b.setVisible(true);//设置显示

         txt=new JTextField();
         txt.setSize(90,30);
         txt.setLocation(10,100);
         txt.setVisible(true);

         mp=new Mypanel();
         mp.setSize(100,30);
         mp.setLocation(100,100);

         JButton jb=new JButton();

         f.add(mp);
         f.add(b);
         f.add(txt);

         f.setLayout(null);
         f.setSize(400, 400);//设置界面大小
         f.getContentPane().setBackground(Color.white);//设置界面的背景颜色
         f.getContentPane().setVisible(true);
         f.setVisible(true);
     }

     public void actionPerformed(ActionEvent e) {
         // TODO Auto-generated method stub

     }
 }

 package javashiyan;

 import java.awt.*;
 import java.util.*;

 public class Mypanel extends Panel {
     public void paint(Graphics g)
     {
         int height = 50;
         int width = 90;
         //验证码框背景颜色
         g.setColor(Color.white);
         //填充验证码背景
         g.fillRect(0, 0, width, height);
         g.setColor(Color.BLACK);
         g.drawRect(0, 0, width-1, height-1);
         Random r = new Random();
         for(int i = 0;i<100;i++)
         {
             int x = r.nextInt(width)-1;
             int y = r.nextInt(height)-1;
             g.drawOval(x, y, 2, 2);//画干扰的圆点
         }
         for(int i=0;i<3;i++)
         {
             int x1=r.nextInt(width)-1;
             int y1=r.nextInt(height)-1;
             int x2=r.nextInt(width)-1;
             int y2=r.nextInt(height)-1;
             g.drawLine(x1, y1, x2, y2);//画干扰的线段
         }

         g.setFont(new Font("黑体",Font.BOLD,20));//设置验证码字体以及大小
         g.setColor(Color.BLUE);//设置验证码字体颜色
         //生成随机验证码
         char[] tmp = ("0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ").toCharArray();
         StringBuilder sb = new StringBuilder();
         for(int i = 0;i<4;i++)
         {
             int pos = r.nextInt(tmp.length);
             char c = tmp[pos];
             sb.append(c + " ");
         }
         g.drawString(sb.toString(), 10, 15);//写入验证码
     }
 }

 package javashiyan;

 import java.util.Random;

 public class main {

     public static void main(String[] args)
     {
             Yanzhen dang=new Yanzhen();
     }

 }