How to get Key ID from PGP public key using bouncy castle library?

Question

I am trying to get key id from PGP public key. After a lot of google search, I found one solution to read public keys using Bouncy Castle java APIs.

Code snippet for same is as follows:

public static PGPPublicKey readPublicKey(InputStream in) throws IOException, PGPException {
        in = org.bouncycastle.openpgp.PGPUtil.getDecoderStream(in);

        PGPPublicKeyRingCollection pgpPub = new PGPPublicKeyRingCollection(in);  

        PGPPublicKey key = null;

        //
        // iterate through the key rings.
        //
        Iterator<PGPPublicKeyRing> rIt = pgpPub.getKeyRings();

        while (key == null && rIt.hasNext()) {
            PGPPublicKeyRing kRing = rIt.next();
            Iterator<PGPPublicKey> kIt = kRing.getPublicKeys();
            while (key == null && kIt.hasNext()) {
                PGPPublicKey k = kIt.next();

                if (k.isEncryptionKey()) {
                    key = k;
                }
            }
        }

        if (key == null) {
            throw new IllegalArgumentException("Can't find encryption(public) key in key ring.");
        }

        return key;
    }

I generated public key using online pgp key generator tool - https://pgpkeygen.com and ran above solution on it. It produced key id in long format.

This worked for older version of jar . However, with new version of jar - bcpg-jdk15on-1.61.jar, it is not working since the constructor to PGPPublicKeyRingCollection now expects KeyFingerPrintCalculator to be provided as argument.

So the line in code,

PGPPublicKeyRingCollection pgpPub = new PGPPublicKeyRingCollection(in); 

needs to be replaced with

PGPPublicKeyRingCollection pgpPub = new PGPPublicKeyRingCollection(in, new JcaKeyFingerprintCalculator());

OR

PGPPublicKeyRingCollection pgpPub = new PGPPublicKeyRingCollection(in, new BcKeyFingerprintCalculator());

I tried with both BC and JCA key finger print calculators, and they both gave same Key ID.

So the questions are,

• Which finger print calculator should be used here?

• Are there any specific scenarios where choosing one over other is relevant/required? I checked javadocs of both calculator classes but there is no much information provided.

• Is there any alternate solution to get key id of a PGP public key in java? If yes, please suggest.

Please note that, I am not generating keys here - those are going to be provided by client and I do not have much information about them.

I am new to public key cryptography implementation in java. Any relevant information related to subject will be highly appreciated.

Thanks.