code: private static String checkP2WPKH(byte[] scriptPubKey) {
  	if ((scriptPubKey.length==22) && (scriptPubKey[0]==0) && (scriptPubKey[1]==0x14)){
  		byte[] keyhash = Arrays.copyOfRange(scriptPubKey, 2, 22);
  		return "P2WPKH_"+BitcoinUtil.convertByteArrayToHexString(keyhash);
  	}
  	return null;
  }
docs: Checks if scriptPubKey is about a transaction for pay-to-witness-public-key-hash (P2WPKH)
  Note that we return only the keyhash, but more information can be found in the witness (cf. https://github.com/bitcoin/bips/blob/master/bip-0141.mediawiki)
  
  
  @param scriptPubKey
  @return null, if transaction is not about P2WPKH, a string starting with "P2WPKH_keyhash"