简单随机密码生成

/**
 * 生成随机密码
 * @param length
 * @return
*/
 public static String getRandomString(int length) { 
 StringBuffer buffer = new StringBuffer("0123456789abcdefghijklmnopqrstuvwxyz"); 
 StringBuffer sb = new StringBuffer(); 
 Random r = new Random(); 
 int range = buffer.length(); 
 for (int i = 0; i < length; i ++) { 
sb.append(buffer.charAt(r.nextInt(range)));
}
 return sb.toString(); 
}

/**
 * 生成随即密码
 * @param pwd_len 生成的密码的总长度
 * @return 密码的字符串
*/
 public static String genRandomNum(int pwd_len){
//35是因为数组是从0开始的，26个字母+10个数字
 final int maxNum = 36;
 int i; //生成的随机数
 int count = 0; //生成的密码的长度
 char[] str = { ‘a‘, ‘b‘, ‘c‘, ‘d‘, ‘e‘, ‘f‘, ‘g‘, ‘h‘, ‘i‘, ‘j‘, ‘k‘,
 ‘l‘, ‘m‘, ‘n‘, ‘o‘, ‘p‘, ‘q‘, ‘r‘, ‘s‘, ‘t‘, ‘u‘, ‘v‘, ‘w‘,
 ‘x‘, ‘y‘, ‘z‘, ‘0‘, ‘1‘, ‘2‘, ‘3‘, ‘4‘, ‘5‘, ‘6‘, ‘7‘, ‘8‘, ‘9‘ };

 StringBuffer pwd = new StringBuffer("");
 Random r = new Random();
 while(count < pwd_len){
//生成随机数，取绝对值，防止生成负数，

 i = Math.abs(r.nextInt(maxNum)); //生成的数最大为36-1

 if (i >= 0 && i < str.length) {
pwd.append(str[i]);
 count ++;
}
}

 return pwd.toString();
}