JConsole!

VisualVM is a tool that provides a visual interface for viewing detailed information about Java applications while they are running on a Java Virtual Machine (JVM). VisualVM organizes JVM data that is retrieved by the Java Development Kit (JDK) tools and presents the information in a way that allows data on multiple Java applications to be quickly viewed—both local applications and applications that are running on remote hosts. Programmers can also capture data about the JVM software and save the data to the local system, and then view the data later or share it with others. VisualVM is built on the NetBeans Platform; its architecture is modular and easy to extend with plugins. »

YourKit Java Profiler is the leading profiling tool in the Java market that delivers the most innovative, powerful and smart performance analysis capabilities. YourKit Java Profiler provides extreme time savings as well as solid assurance features. Most of its features are not simply unrivaled but absolutely unique.

The Eclipse Memory Analyzer is a fast and feature-rich Java heap analyzer that helps you find memory leaks and reduce memory consumption.

JProfiler is the leading Java Profiler for profiling on the JVM. JProfiler's intuitive UI helps you resolve performance bottlenecks, pin down memory leaks and understand threading issues.