import java.lang.instrument.Instrumentation;

public class ObjectSizeFetcher {

private static Instrumentation instrumentation;

public static void premain(String args, Instrumentation inst) {

instrumentation = inst;

}

public static long getObjectSize(Object o) {

return instrumentation.getObjectSize(o);

}

}

public class C {

private int x;

private int y;

public static void main(String [] args) {

System.out.println(ObjectSizeFetcher.getObjectSize(new C()));

}

}

Try this, this works for me.

http://sizeof.sourceforge.net

Download it.

Unzip it.

Add jar file to your project

In Netbeans Go to properties of your project.

Go to run.

Add this to VM Argument ==>  -javaagent:/path of where you save your SizeOf.jar/sizeOf.jar

To test create any object.e.g., Class1 obj = new Class1();

System.out.println("Object size" + SizeOf.sizeOf(obj));

Result: Depend on size of your object

Object size = 8 

I believe a better explained answer to this question can be found at: http://www.kogonuso.com/2015/04/how-to-estimate-java-object-sizes-with.html

It is possible that standard jdk tools for visual memory control, such as jconsole, are better choice for your task.

The answer given by Sanjay is as close as it gets, but also have a good glance through the JavaWorld article on Sizeof for Java.

http://www.javaworld.com/article/2077408/core-java/sizeof-for-java.html