how to profile java application using visualVM?

Question

My boss wants me to profile our product application to see if we can get some improvement with regard to memory usage. When I profile the memory, I get this:

What's the meaning of the last column ("Generations")? How can I analysis the application using this information?

Answer 1

Concerning the "generations" column:

VisualVM comes with your Sun JDK6 for free, originates from Netbeans, look for jvisualvm in JAVA_HOME/bin. It incorporates a memory profiler that uses a metric called “surviving generations” (or short “generations”). So what is a surviving generation? Surviving generations: The number of different ages for all objects allocated on the JVM heap since the profiling session started. Age of object: The age of the object is the number of garbage collections the object has survived.

Extracted from http://www.munzandmore.com/2011/ora/memleak

About how to analyze the data, it's a broad subject. I suggest you to take a look at this:

http://my.safaribooksonline.com/book/programming/java/9780137001040

Answer 2

Surviving generations are explained in this blog post.