### Question:
PGP { public static String formatFingerprint(String fingerprint) { StringBuilder fpr = new StringBuilder(); int length = fingerprint.length(); for (int i = 0; i < length; i += 4) { fpr.append(fingerprint.substring(i, i + 4)); if (i < (length - 4)) { fpr.append(' '); if (i == (length / 2 - 4)) fpr.append(' '); } } return fpr.toString(); } private  PGP(); static void registerProvider(); static PGPDecryptedKeyPairRing create(Date timestamp); static PGPKeyPairRing store(PGPDecryptedKeyPairRing pair,
            String id,
            String passphrase); static PGPPublicKey revokeKey(PGPKeyPair secret); static PGPDecryptedKeyPairRing fromParcel(Parcel in); static void toParcel(PGPDecryptedKeyPairRing pair, Parcel dest); static void serialize(PGPDecryptedKeyPairRing pair, ObjectOutputStream dest); static PGPDecryptedKeyPairRing unserialize(ObjectInputStream in); static String getFingerprint(PGPPublicKey publicKey); static String getFingerprint(byte[] publicKeyring); static String formatFingerprint(String fingerprint); static String createFingerprintURI(String fingerprint); static String getUserId(PGPPublicKey key, String host); static String getUserId(byte[] publicKeyring, String host); static PGPUserID parseUserId(byte[] publicKeyring, String host); static PGPUserID parseUserId(PGPPublicKey key, String host); static int getKeyFlags(PGPPublicKey key); static PGPPublicKey getMasterKey(PGPPublicKeyRing publicKeyring); static PGPPublicKey getMasterKey(byte[] publicKeyring); static PGPPublicKey getAuthenticationKey(PGPPublicKeyRing publicKeyring); static PGPPublicKey getSigningKey(PGPPublicKeyRing publicKeyring); static PGPPublicKey getEncryptionKey(PGPPublicKeyRing publicKeyring); static PGPPublicKeyRing readPublicKeyring(byte[] publicKeyring); static PrivateKey convertPrivateKey(PGPPrivateKey key); static PrivateKey convertPrivateKey(byte[] privateKeyData, String passphrase); static PublicKey convertPublicKey(PGPPublicKey key); static byte[] changePassphrase(byte[] privateKeyData, String oldPassphrase, String newPassphrase); static PGPSecretKeyRing copySecretKeyRingWithNewPassword(byte[] privateKeyData,
            String oldPassphrase, String newPassphrase); static PGPSecretKeyRing copySecretKeyRingWithNewPassword(PGPSecretKeyRing secRing,
            String oldPassphrase, String newPassphrase); static Provider PROVIDER; }### Answer:
@Test public void testFormatFingerprint() throws Exception { String fpr = PGP.formatFingerprint("F28947756EB27311E86F6309274BE2A3BD56E37A"); assertEquals("F289 4775 6EB2 7311 E86F 6309 274B E2A3 BD56 E37A", fpr); }