VisualVM

VisualVM is a tool to monitor and troubleshoot Java applications. It runs on Oracle/Sun JDK 6, but is able to monitor applications running on JDK 1.4 and higher.

It utilizes various available technologies like jvmstat, JMX, the Serviceability Agent (SA), and the Attach API to get the data and automatically uses the fastest and most lightweight technology to impose minimal overhead on monitored applications.

With the out-of-the-box features it perfectly fits all the requirements of application developers, system administrators, quality engineers and - last but not least - application users submitting bug reports containing all the necessary information.