Java SE 6 has already been released for quite some time (ya… now already update 7 looo). Even though many monitoring and diagnostics features are enhanced and introduced in Java 6, but it has been lacking an out-of-the-box bundling of a convincing visual Java application monitoring or profiling tool, until the most recent JDK6 Update 7.
In this latest update of JDK 6 (version 6u7), the Java VisualVM - a visual tool integrating several lightweight profiling capabilities for troubleshooting Java applications, is bundled. After installation of JDK 6u7, you can find jvisualvm.exe in the /bin folder. By the way, VisualVM is similar to JConsole to certain extends, but a lot better than JConsole.
You might have heard of JProfiler, or even have some first-hand experiences with it. No doubt it’s an comprehensive Java application profiler, but it comes with a price tag 
Java VisualVM is FREE, free like a free beer!
How to take advantage with Java VisualVM?
Firstly, in order to benefit from the full profiling advantage of Java VisualVM, you must run your Java application on JVM 6. No worry, you can also compile your codes with Java 5 compatibility, and run the application on JVM 6, so that it is profilable by VisualVM.
For all applications running on JVM 6, you will be able to create CPU and memory profiler, take thread dumps, browse heap dumps, and more. For applications running on JVM 5, the most that you can monitor with VisualVM, is only the threads. Click here for more details on Java VisualVM features.
Actually, the diagnostics and monitoring features presented by VisualVM is nothing new. They are all available since day 1 when Java 6 was released. However, VisualVM integrates various capabilities and tools available, and present in a more visually readable format.
Can you imagine how useful it is when you can actually tell how much memory is occupied by each and every class when your application is running? Yes, exactly each and every class. You can even filter by package or class name to specifically monitor a targeted portion of your application performance. When application is running slow on a specific web page, VisualVM can help you to trace which exact class is the culprit, and you can focus your fine-tuning and tweaking on this class.
However, you’re not recommended to profile live application (with real users actively using it) with VisualVM, as profiler is known to impose performance overhead on the application. You can use load testing tool like JMeter to simulate the load if needed.
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