CODEWITHSUNDEEP
javaoptimizationmemory-management
Anis H
Anis H

Reputation: 1150

How to minimize the memory used by my application?

I'm writing a Java/Swing application with ~30 class my probleme is when i run my programe it load more than 150 M of the memory, is that normal ? since the application have 4 threads, parse some XML files, load some icon file, and drow some Jfreechat charts. if not how can i do to minimize the amount of memory used by the application, is affecting some variables to null help? is loading the XML files once to use them in all the application life cycle help or i have to load them evry time i need them? is there some other tips that help me?

PS: im devlopping with a 8G memory computer in case that can affect the memory used by my program.

EDIT: it appeared that the program don't occupy all the 150MB because i get this value from the top command on linux, by running this code in my application as vilmantas advises me:

   long free = Runtime.getRuntime().freeMemory();
   long total = Runtime.getRuntime().totalMemory();
   long max = Runtime.getRuntime().maxMemory();
   long used = total - free;

I found that he occupy much less than that (~40MB) so i decide to run it with "-Xmx40M" argument and i reduce more than 40% of memory usage in the Top command. The problem who are occupying the rest of memory since JVM (as i know) have his own process ? and how to make this operation automatic**?** because when choosing a not appropriate value you can get a memory exception as i have by running with "-Xmx30M" argument:

   Exception in thread "Thread-2" java.lang.OutOfMemoryError: Java heap space

Upvotes: 3

Views: 3220

Answers (4)

sulai
sulai

Reputation: 5354

You could use java memory heap analyzer like http://www.eclipse.org/mat/ to identify the parts of your application that use up most of the memory. You can then either optimize your data structures, or decide release parts of the data by setting all references to it to null.

Unintended references to data that is not needed anymore are also refered as "memory leaks". Settings those references to null will cause the garbage collector to remove it from java memory heap.

Along that line, you might find WeakReferences helpful.

Upvotes: 2

Vilmantas Baranauskas
Vilmantas Baranauskas

Reputation: 6726

Where do you observe those 150M? Is that how much your JVM process occupies (e.g. visible in the top command on linux/unix) or is it really the memory used (and necessary) by your application?

Try writing the following 4 values when your application runs:

    long free = Runtime.getRuntime().freeMemory();
    long total = Runtime.getRuntime().totalMemory();
    long max = Runtime.getRuntime().maxMemory();
    long used = total - free;

If the value for "used" is much lower than 150M, you may add java start parameter e.g. "-Xmx30M" to limit the heap size of your application to 30MB. Note that the JVM process will still occupy a little bit more than 30MB in such case.

The memory usage by JVM is somewhat tricky.

Upvotes: 1

yair
yair

Reputation: 9245

Setting variables to null can help preventing memory leaks, if the referring variable's life cycle is greater than the referred instance. So that variables that should hold-on through the whole application life cycle are better not hold references to temporary objects that are used for a short time.

Loading the XMLs only once can help if you're good with loading its information only once. Meaning, if the XML is changed otherwise than through your application and you need to get the update - you'll have to reload the XML (and if the deprecated XML info is no longer needed - get rid of it).

Upvotes: 3

unexpectedvalue
unexpectedvalue

Reputation: 6139

It is. This is Java, usually your VM/GC will do the job for you. Worry about memory usage when and if it becomes a problem.
If you want, there are several tools that can help you analyze what is going on. How to monitor Java memory usage?

Upvotes: 4

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