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How can i get size of a class?

is there any way to find a size of class? likesizeof(struct stu) in c language
[92 byte] By [hai_karuppaIyana] at [2007-11-26 20:26:36]
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# 1

I think that cannot be done directly as in C/C++ .. But u can use the concept of classLoader .

You may summ up the no of bytes they occupy.. and for object references take the size as long variable. U can do this only by this way.. No direct way is available to my knowledge. If u find any other way pls let us know..

Shree_sdrajana at 2007-7-10 0:53:36 > top of Java-index,Desktop,Runtime Environment...
# 2

Yes you can with 1.5 using http://java.sun.com/j2se/1.5.0/docs/api/java/lang/instrument/Instrumentation.html

It is not straight forward process. You have to create your own agent:

package foocompany.agent;

public class SimpleAgent {

private static Instrumentation instrumentation;

/** Creates a new instance of SimpleAgent */

public SimpleAgent() {

}

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

instrumentation = inst;

}

public static long sizeOf(Object object) {

return instrumentation.getObjectSize(object);

}

}

Create a manifest file:

Manifest-Version: 1.0

Premain-Class: foocompany.agent.SimpleAgent

Combine them into a jar file.

And then specify the jar file on the command line:

java -javaagent:"<path to jar>\simpleagent.jar" <rest of arguments...>

Then you can call SimpleAgent.sizeOf() on any object from your program.

Caffeine0001a at 2007-7-10 0:53:36 > top of Java-index,Desktop,Runtime Environment...
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