### Question:
Sign { public static BigInteger publicKeyFromPrivate(BigInteger privKey) { ECPoint point = publicPointFromPrivate(privKey); byte[] encoded = point.getEncoded(false); return new BigInteger(1, Arrays.copyOfRange(encoded, 1, encoded.length)); }  static SignatureData signMessage(byte[] message, ECKeyPair keyPair); static BigInteger signedMessageToKey(
            byte[] message, SignatureData signatureData); static BigInteger publicKeyFromPrivate(BigInteger privKey);  }### Answer:
@Test public void testPublicKeyFromPrivateKey() { assertThat(Sign.publicKeyFromPrivate(SampleKeys.PRIVATE_KEY), equalTo(SampleKeys.PUBLIC_KEY)); }