public String getKmsMasterKeyId() {
        return this.kmsMasterKeyId;
    }
<p>
The Amazon Resource Name (ARN) or unique identifier (key ID) for the KMS key that's used by default to encrypt
objects that are added to the bucket. This value is null if the bucket is configured to use an Amazon S3 managed
key to encrypt new objects.
</p>

@return The Amazon Resource Name (ARN) or unique identifier (key ID) for the KMS key that's used by default to
        encrypt objects that are added to the bucket. This value is null if the bucket is configured to use an
        Amazon S3 managed key to encrypt new objects.
aws-java-sdk-macie2/src/main/java/com/amazonaws/services/macie2/model/BucketServerSideEncryption.java