AppDynamics is the very first free product designed for troubleshooting java performance while getting full visibility in production environments. http://www.appdynamics.com/products-free-download.php
Plumbr is a memory leak detection tool. It monitors your Java application, detects if it leaks memory and reports its findings to you with precise instructions on where the leaking occurs. You have to change nothing in your application/source code/deployment plan in order to get advantage from using Plumbr.