code: public void verifyMessage(String message, String signatureBase64) throws SignatureException {
          ECKey key = ECKey.signedMessageToKey(message, signatureBase64);
          if (!key.pub.equals(pub))
              throw new SignatureException("Signature did not match for message");
      }
docs: Convenience wrapper around {@link ECKey#signedMessageToKey(String, String)}. If the key derived from the
  signature is not the same as this one, throws a SignatureException.