How to use java heap profilers (HPROF)

Question

With the basic knowledge of java 'hprof', I tried executing the below command as per oracle docs

java -agentlib:hprof Hello.class

But i get the below error instead of the profiling information

Caused by: java.lang.ClassNotFoundException: Hello.class
    at java.net.URLClassLoader$1.run(URLClassLoader.java:200)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:307)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:252)
    at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:320)

Can someone illustrate on how should hprof be used properly so as to get the profiling information ?

Jean-François Savard · Accepted Answer · 2015-02-02T18:45:14.937

2

You just need to remove the .class at the end of the class as Java by default will search for class files.

java -agentlib:hprof Hello

However, to get the heap allocation profile you need to add some parameters...

java -agentlib:hprof=heap=sites Hello

For more information type

java -agentlib:hprof=help

And visit http://docs.oracle.com/javase/8/docs/technotes/samples/hprof.html

edited Feb 02 '15 at 18:45

answered Feb 02 '15 at 17:41

Jean-François Savard

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I tried running the command for classes located in other folders. I get the same exception along with the message 'Could not find the main class'. Any idea how to resolve this? – Aarish Ramesh Feb 02 '15 at 18:02
@aarish When running a `java` program, you can only call the Main file (the one which contains the `main` method). This is why you get this error. – Jean-François Savard Feb 02 '15 at 18:05
The java program contains the main method – Aarish Ramesh Feb 03 '15 at 07:32
@aarish then make sure you typed it correctly and that the main method declaration is `public static void main(String args[])` – Jean-François Savard Feb 03 '15 at 13:52

How to use java heap profilers (HPROF)

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