private static final void validate(AesGcmParameters parameters) throws GeneralSecurityException {
    if (parameters.getKeySizeBytes() == 24) {
      throw new GeneralSecurityException("192 bit AES GCM Parameters are not valid");
    }
  }
This key manager generates new {@code AesGcmKey} keys and produces new instances of {@code
AesGcmJce}.
java_src/src/main/java/com/google/crypto/tink/aead/AesGcmKeyManager.java