Memory footprint minimization in Java EE 5, for classes, primitive data types and Strings

Question

Context is: Java EE 5.

I have a server running some huge app. I need to refactor the classes, so that their memory footprint is low (towards lowest possible), in exchange for CPU time (of which there's plenty).

I already know of ways to use bit operations to stuff multiple booleans, shorts or bites into an int (for example).

I'd need from you other optimization ideas, like, what do i do with Strings, what collections are better to use, and anything else that you happen to know.

Thx, you guys rule!

Answer 1

This pdf about memory efficiency in java might be of interest to you.

Especially the standard collections seem to be huge memory wasters. But the first step before doing any micro-optimizations would be to profile your application, create heap dumps and analyze these.

Answer 2

A couple of things to consider

• If you are done with an object and it will remain in scope, set it to null
• Use StringBuilder (or StringBuffer if you need thread safety) instead of concatenating Strings.

However, if your memory usage is such an issue it may be an architectural problem with the code.