NPE when calling getObjectSize()

Question

In reference to : Calculate size of Object in Java

I tried to run this program and get the size of the object created

  //main 
 while(true){
        Integer x=new Integer(50);
        System.out.println("HashCode of this object="+x.hashCode()+" 
                  ,  with Size of "+ObjectSizeFetcher.getObjectSize(x));
        i++;
}

 The output -- NullPointerException is thrown when getObjectSize() is invoked.

   new Integer() -->

should have created a new wrapper object. Instead it creates NPE. Why ?

java version "1.6.0_65" Apple OSX - 10.9.1 --Ignore Syntax errors

That `ObjectSizeFetcher` requires that it be run as an agent. See http://docs.oracle.com/javase/6/docs/api/java/lang/instrument/package-summary.html for details. — SamYonnou, Jan 22 '14 at 14:52
Did you follow all the steps in [this answer](http://stackoverflow.com/a/52682/1343161)? — Keppil, Jan 22 '14 at 14:53

score 1 · Accepted Answer · answered Jan 22 '14 at 14:58

1

Because the static field ObjectSizeFetcher.instrumentation was null when you called ObjectSizeFetcher.getObjectSize(x).

You should call method ObjectSizeFetcher.premain(String args, Instrumentation inst) before, with a non-null inst argument.

answered Jan 22 '14 at 14:58

Bludzee

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NPE when calling getObjectSize()

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