private static Map<String, Parameters> namedParameters() throws GeneralSecurityException {
        Map<String, Parameters> result = new HashMap<>();
        result.put("AES128_GCM", PredefinedAeadParameters.AES128_GCM);
        result.put(
            "AES128_GCM_RAW",
            AesGcmParameters.builder()
                .setIvSizeBytes(12)
                .setKeySizeBytes(16)
                .setTagSizeBytes(16)
                .setVariant(AesGcmParameters.Variant.NO_PREFIX)
                .build());
        result.put("AES256_GCM", PredefinedAeadParameters.AES256_GCM);
        result.put(
            "AES256_GCM_RAW",
            AesGcmParameters.builder()
                .setIvSizeBytes(12)
                .setKeySizeBytes(32)
                .setTagSizeBytes(16)
                .setVariant(AesGcmParameters.Variant.NO_PREFIX)
                .build());
    return Collections.unmodifiableMap(result);
  }
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