java.lang.NullPointerException when using Java with Ruby -

i trying call ruby function in java. got nullpointerexception when run program.
here java code

import java.io.ioexception; import java.io.inputstreamreader; import java.io.reader; import javax.script.invocable; import javax.script.scriptengine; import javax.script.scriptenginemanager; import javax.script.scriptexception; import java.io.inputstream;  public class myprogram {  public static void main(string[] args) throws ioexception, nosuchmethodexception      {         try         {             scriptenginemanager mgr = new scriptenginemanager();             scriptengine rbengine = mgr.getenginebyextension("rb");              inputstream = classloader.getsystemresourceasstream("src/myruby.rb");             reader reader = new inputstreamreader(is);             rbengine.eval(reader);             invocable invocableengine = (invocable)rbengine;              if (invocableengine != null)             {                 int set = (integer) invocableengine.invokefunction("myfunc",6,6);             }          }         catch (scriptexception e)         {             system.out.println("\nscriptexception = "+e);         }     } } 

and myruby.rb file contains

def myfunc(a,b)   f=a+b   return f end 

the error getting is,

exception in thread "main" java.lang.nullpointerexception     @ java.io.reader.<init>(unknown source)     @ java.io.inputstreamreader.<init>(unknown source)     @ myprogram.main(myprogram.java:22)   

please me find problem.
in advance.

inputstream = classloader.getsystemresourceasstream("src/myruby.rb"); 

here, is null.

try absolute path open file.

if file found, there problem classloader.getsystemresourceasstream.