Monitoring memory consumption by different java objects

Question

If we have 300 classes in an application, is it possible to monitor how many instances of each class we have at a given time? Is it possible to know how much memory each instance is consuming?

Thanks

Answer 1

use jvisualvm.exe it is part of the JDK6

Answer 2

You could use a Java profiler, depending on which web container (if it's a web-app) you're deploying to you can try alot of different profilers: http://java-source.net/open-source/profilers

Answer 3

JDK 1.6 includes a tool called jvisualvm, which allows you to view lots of information about your running Java program, including memory usage, threads, etc. You could also use a profiler to see this kind of information. The profiler in NetBeans looks a lot like JVisualVM.

Answer 4

Most profilers will give you this information. I'm personally familiar with JProfiler, but I expect any worthwhile profiler would let you do this.

For a more low-tech solution, you could even trigger a heap dump from your application and then look through it with an application like jhat. The interface leaves a lot to be desired, though, and profilers would be much more comfortable to use in any non-trivial case.

Edit: here is an example of the memory screen for JProfiler, and you can also investigate the reference chain.

Answer 5

I personally like Yourkit. It has a very good UI and comes with a 30 day trial. The details are also pretty extensive.

The online help document in that site should help you on how to set things up for running it.

Answer 6

use profiler4j or pmd

personally i like profiler4J for its ease of use and simple graphics :)