java 生成随机密码

/**
* 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();
}