Finding Memory Usage in Java

Question

Following is the scenario i need to solve. I have struck with two solutions.

I need to maintain a cache of data fetched from database to be shown on a Swing GUI. Wheneve

Answer 1

Very late after the original post, I know, but I thought I'd post an example of how I've done it. Hopefully it'll be of some use to someone (I stress, it's a proof of principal example, nothing else... not particularly elegant either :) )

Just stick these two functions in a class, and it should work.

EDIT: Oh, andimport java.util.ArrayList; import java.util.List;

public static int MEM(){
    return (int)(Runtime.getRuntime().maxMemory()-Runtime.getRuntime().totalMemory() +Runtime.getRuntime().freeMemory())/1024/1024;
}

public static void main(String[] args) throws InterruptedException
{
    List list = new ArrayList();

    //get available memory before filling list
    int initMem = MEM();
    int lowMemWarning = (int) (initMem * 0.2);
    int highMem = (int) (initMem *0.8);


    int iteration =0;
    while(true)
    {
        //use up some memory
        list.add(Math.random());

        //report
        if(++iteration%10000==0)
        {
            System.out.printf("Available Memory: %dMb \tListSize: %d\n", MEM(),list.size());

            //if low on memory, clear list and await garbage collection before continuing
            if(MEM()

EDIT: This approach still relies on sensible setting of memory in the jvm using -Xmx, however.

EDIT2: It seems that the gc request line really does help things along, at least on my jvm. ymmv.