private static final char HEX_DIGITS[] = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
    'A', 'B', 'C', 'D', 'E', 'F' };
public static String toHexString(byte[] b) {
  //String to byte
  StringBuilder sb = new StringBuilder(b.length * 2);
  for (int i = 0; i < b.length; i++) {
    sb.append(HEX_DIGITS[(b[i] & 0xf0) >>> 4]);
    sb.append(HEX_DIGITS[b[i] & 0x0f]);
  }
  return sb.toString();
}
public String md5(String s) {
  try {
    // Create MD5 Hash
    MessageDigest digest = java.security.MessageDigest.getInstance("MD5");
    digest.update(s.getBytes());
    byte messageDigest[] = digest.digest();
    return toHexString(messageDigest);
  } catch (NoSuchAlgorithmException e) {
    e.printStackTrace();
  }
  return "";
}