Runtime heap size set in Eclipse

Question

public class Test {
        public static void main(String[] args) {
            long heapsize = Runtime.getRuntime().totalMemory();
            System.out.println("heapsize is :: " + heapsize/(1024*1024));
        }

}

The output is:

heapsize is :: 245

Does this mean my runtime has only 245M memory? My computer has 8GB memory. I doubt output this is correct, since the running of Eclipse alone will consume a lot more than 245M.

In Eclipse, I click Windows->Preferences->Java->Installed JREs, and set Default JVM arguments as follows:

-ea -Xms256m -Xmx4096M

Then run the test again. It still prints out the same number, 245. How could this happen?

Edited: from Java doc for Runtime.getRuntime().totalMemory():

Returns the total amount of memory in the Java virtual machine. 
The value returned by this method may vary over time, depending on the 
host environment.

Runtime heap size set in Eclipse

1 Answers