@Override
    protected AmazonElasticFileSystemAsync build(AwsAsyncClientParams params) {
        return new AmazonElasticFileSystemAsyncClient(params);
    }
Construct an asynchronous implementation of AmazonElasticFileSystemAsync using the current builder configuration.

@param params
       Current builder configuration represented as a parameter object.
@return Fully configured implementation of AmazonElasticFileSystemAsync.
aws-java-sdk-efs/src/main/java/com/amazonaws/services/elasticfilesystem/AmazonElasticFileSystemAsyncClientBuilder.java