package com.coding.day4;

public class 不重复验证码 {
	public static String generateRandomStr(int len) {
	    String code = "0123456789qwertyuiopasdfghjklzxcvbnmQWERTYUIOPASDGFHJKLZXCVBNM";//定义字符源
	    String str = "";
	    for (int i=1; i<=4; i++) {
	    
	        //循环随机获得当次字符，并移走选出的字符
	        String num = String.valueOf(code.charAt((int) Math.floor(Math.random() * code.length())));
	        str += num;
	        code = code.replaceAll(num,"");//将已选字符格式化
	    }
	    return str;
	}
	 
	public static void main(String[] args) {
	    for (int i = 1; i < 2; i++) {
	        System.out.println("验证码为："+generateRandomStr(4));
	    }
	}
}