生成4位随机验证码工具类

keyUtil：

package com.duocy.util;

import java.util.Random;

public class keyUtil {
public String keyUtil() {
String str="ABCDEFGHIJKLMNOPQRSTUVWXYZqwertyuiopasdfghjklzxcvbnm0123456789";
StringBuilder st=new StringBuilder(4);
for(int i=0;i<4;i++){
char ch=str.charAt(new Random().nextInt(str.length()));
st.append(ch);
}
String findkey=st.toString().toLowerCase();
System.out.println("生成找回的key为："+st.toString());
return findkey;
}
}

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