The AWS Common Runtime (CRT)-based SDK client and the Transfer Manager for Amazon Simple Storage Service (Amazon S3) are now generally available in the AWS SDK for Java 2.x. The CRT-based S3 client is intended for users who want maximized throughput when transfering objects to and from Amazon S3, and the S3 Transfer Manager is a high level transfer utility built on top of CRT-based S3 cleint and provides additional functionalities such as file directories transfer and progress monitoring.
Source:: Amazon AWS