Understanding performance of Java code is hard, because the actually executed program is created on-the-fly by JIT compiler.
JITWatch is a log analyser for Java HotSpot JIT compiler. It consumes JIT log files and visualizes the compilation activity.
This post describes how to get started with JITWatch a project and what statistics are immediately useful to look at.
JITWatch is an excellent tool that gives a visual feedback about what is happening within your application for anyone who is interested in JVM performance.
Read the full how-to article on RebelLabs: http://zeroturnaround.com/rebellabs/why-it-rocks-to-finally-understand-java-jit-with-jitwatch/