Memory Leakage due to HashMap

Question

I am facing memory leakage because of HashMap in my code. When I first login to the application this HashMap populate and I use this Map to cache some data.

I used this cached Data several places in my application.

Its size grows continuously after Login when nothing is running in the application. The size decreases only in the situation when the garbage collector is called automatically or I call that.

But after that it again starts increasing. It is a memory leak for sure but how can I avoid it?

My profiler also showing ResultSet.getString() and Statement.execute() as the hotspot memory allocation. these methods used to populate this cache.

Is the memory leak there because of these methods? I have close the DB Connection in finally block.

Why it is still showing me these methods?

Answer 1

As the comments above explain, this does not sound like a memory leak.

In a java application, the JVM will create objects and use up memory. As time goes on, some of the objects will go out of scope (become eligible for garbage-collection) but until the next collection happens, they will still be in the heap, 'using up memory'. This is not a problem, it is how java works. When the JVM decides it needs to free up memory, it will run a collection and the used memory should drop.

Should you care about what you are seeing? I can think of two reasons you should and one you why shouldn't. If your garbage-collections free up enough memory for the application keep running, the collections do not affect performance and you are a busy person with other things to do, then I see no reason why you should care.

If however, you are worried that you do not understand how the application works in detail, or you have a reason why "so much memory" is an issue (you will want to run the application with even more data in future, or will want to run it with less heap assigned in future), then you may want to investigate.

If the memory is being used up when the application is doing nothing, then I would focus on that. What is it really doing when it is doing 'nothing'? I bet it's doing 'something'