Check available heapSize programmatically?

I am using Eclipse. The problem is my application crashes if the allocated memory is less then 512MB. Now is there anyway to check the available memory for a program before starting heavy memory exhaustive processing? For example, I know we can check available JVM heap size as:

long heapSize = Runtime.getRuntime().totalMemory(); System.out.println("Heap Size = " + heapSize); 

Problem is, this gives the JVM heap size. Even increasing it does not work using Eclipse. In Eclipse, if I change the VM arguments then it works. However the printout from above statements is always the same. Is there any command through which I can exactly know how much memory I am allocated for a particular application?

1 Answer

You could use JMX to collect the usage of heap memory at runtime.

Code Example:

import java.lang.management.ManagementFactory; import java.lang.management.MemoryPoolMXBean; import java.lang.management.MemoryType; import java.lang.management.MemoryUsage; for (MemoryPoolMXBean mpBean: ManagementFactory.getMemoryPoolMXBeans()) { if (mpBean.getType() == MemoryType.HEAP) { System.out.printf( "Name: %s: %s\n", mpBean.getName(), mpBean.getUsage() ); } } 

Output Example:

Name: Eden Space: init = 6619136(6464K) used = 3754304(3666K) committed = 6619136(6464K) max = 186253312(181888K) Name: Survivor Space: init = 786432(768K) used = 0(0K) committed = 786432(768K) max = 23265280(22720K) Name: Tenured Gen: init = 16449536(16064K) used = 0(0K) committed = 16449536(16064K) max = 465567744(454656K) 

If your have question about "Eden Space" or "Survivor Space", check out How is the java memory pool divided