Java Client for MQTT using AWS IoT

I am fairly new to the Aws IoT . I am aware that we can write the Java client for Aws IoT .
I have below three queries ,
1)Is the Java Client used only to receive messages from the 'Thing' on Aws ?
2)Can other devices subscribe to the Java Client
3)Can this client also send messages to other devices

It will be helpful if you could help out with the starting point to implement the java. References to any articles or links would really helpful