private AWSKMSClient newAWSKMSClient(
            AWSCredentialsProvider credentialsProvider,
            ClientConfiguration clientConfig,
            CryptoConfiguration cryptoConfig,
            RequestMetricCollector requestMetricCollector
    ) {
        final AWSKMSClient kmsClient = new AWSKMSClient(
            credentialsProvider, clientConfig, requestMetricCollector);
        final Region kmsRegion = cryptoConfig.getAwsKmsRegion();
        if (kmsRegion != null)
            kmsClient.setRegion(kmsRegion);
        return kmsClient;
    }
Creates and returns a new instance of Amazon Web Services KMS client in the case when
an explicit Amazon Web Services KMS client is not specified.
aws-java-sdk-s3/src/main/java/com/amazonaws/services/s3/AmazonS3EncryptionClient.java