public static String getRandomString(int length) {
final String s = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
SecureRandom sr = new SecureRandom();
StringBuilder sb = new StringBuilder(length);
for (int i = 0; i < length; i++) {
sb.append(s.charAt(sr.nextInt(s.length())));
}
return sb.toString();
}