随机生成字符串

随机生成4位验证码： public String createCode(){    String str = "0,1,2,3,4,5,6,7,8,9";       String str2[] = str.split(",");//将字符串以,分割       Random rand = new Random();//创建Random类的对象rand       int index = 0;       String randStr = "";//创建内容为空字符串对象randStr           for (int i=0; i<4; ++i){  //i<6:6位验证码            index = rand.nextInt(str2.length-1);//在0到str2.length-1生成一个伪随机数赋值给index              randStr += str2[index];//将对应索引的数组与randStr的变量值相连接           }       return randStr; }//生成随机的字符串（长度为6，包含字母，包含数字）RandomStringUtils.random(6, true, true)