java 练习之生成随机四位验证码

java 小demo — 随机生成四位验证码

import javax.swing.*;
import java.awt.*;
import java.util.Random;
/**
 * @author yk.ddm
 * @createDate 2021-01-05 12:18
 */

public class Test {

    public static void main(String[] args) {
        JFrame jf = new JFrame();
        JPanel jPanel = new Mypanel();
        jf.add(jPanel);
        jf.setSize(200,100);
        jf.setLocationRelativeTo(null);
        jf.setVisible(true);
        Mypanel mypanel =new Mypanel();
        Test05 t = new Test05();
        String s = t.getNumber();
    }
}

class Mypanel extends JPanel{
    static String s;
    @Override
    public void paint(Graphics g) {
        //设置验证码的宽高
        int width = 160;
        int height = 40;
        g.setColor(Color.LIGHT_GRAY);//背景颜色
        g.fillRect(0, 0, width -1, height -1);//背景填充
        g.setColor(Color.BLACK);//边框颜色
        g.drawRect(0, 0, width -1, height -1);//绘制边框
        //绘制干扰点
        Random random = new Random();
        for (int i = 0; i < 100; i++) {
            int x = random.nextInt(width) - 2;
            int y = random.nextInt(height) - 2;
            g.drawOval(x, y, 2, 2);
        }
        //开始对验证码字体进行设置
        g.setFont(new Font("黑体",Font.BOLD,32));//字体
        g.setColor(Color.BLUE);//颜色
        //设置一个数组来当验证码的词库
        char [] arr = ("0123456789").toCharArray();
        //实例化一个StringBuilder对象来生成随机验证码
        StringBuilder sb = new StringBuilder();
        //循环生成4个随机数
        for (int i = 0; i < 4; i++) {
            //生成一个随机位置
            int position = random.nextInt(arr.length);
            //获取到这个位置的字符
            char c = arr[position];
            //将字符添加到StringBuilder对象里面,并且加一个空格保持间隔
            sb.append(c+"");
        }
        //写入验证码，调用sb的toString()方法将其转换为一个String对象进行写入
        g.drawString(sb.toString(), 20, 30);
        //新建一个String类型的变量来存储已经好了的验证码，用来判断用户输入的验证码是否正确
        String s = sb.toString();
        this.s = sb.toString();
//        Mypanel.s = sb.toString();
        System.out.println(Mypanel.s);

//        System.out.println(s);
        Test05 t = new Test05();
        t.setNumber(s);
    }
}

class Test05 {
    String Number ;
    public String getNumber() {
        return Number;
    }
    public void setNumber(String number) {
        Number = number;
    }
}

标签：java,String,int,验证码,sb,new,四位,Mypanel
来源： https://blog.csdn.net/yk_ddm/article/details/112226075