验证码（正则表达式）

package term;

import java.util.Random;
import java.util.regex.Pattern;


public class Demo {

    private int len;
    private String  s= "qwertyuiopasdfghjklzxcvbnm1234567890";

    public Demo(){
        this.len = 4;
    }

    public Demo(int len){
        this.len = len;
    }

    public static void main(String[] args) {
        Demo d = new Demo();
        System.out.println(d.getCode());
    }

    //生成验证码并返回
    public String getCode(){
        Random r = new Random();
        StringBuilder  getS = new StringBuilder();
        char[] arr = new char[len];

        //正则校验
        String jyCode = "[0-9][a-z][0-9][a-z]{5}";

        while (true) {
            for (int i = 0; i < len; i++) {
                arr[i] = s.charAt(r.nextInt(s.length()));
                getS.append(arr[i]);
            }
            if(Pattern.matches(jyCode,getS))   //使用matches方法进行 匹配对比 成功返回
                break;
                getS.delete(0,getS.length());  //失败 删除后重新随机
        }
        return getS.toString();
    }
}

package term;

import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class Test {
    public static void main(String[] args) {


        String s = "$1231cxzcd$13";

        //先创建一个Pattern 对象 模式
        Pattern pattern = Pattern.compile("[$][0-9]+");

        //再创建一个匹配器对象
        Matcher matcher = pattern.matcher(s);

        //public boolean find() 判断是否有 满足正则表达式的内容
        String[] arry = {};
        int i = 0;
        while (matcher.find()){
            //public String group(int group) 返回满足正则表达式内容
            System.out.println("有"+matcher.group(0));
            arry[i] = matcher.group(0);
            i++;
        }
    }
}