Re: [Jython-users] Threads:-java.lang.ExceptionInInitializationError:java.lang.NullPointerException

[<bc...@wo...>]

[rohit seth]

>I am getting
>"java.lang.ExceptionInInitializationError:
>java.lang.NullPointerException
>at
>org.Python.core.PySystemState.<init>(PySystemState.java:158)
>at
>org.Python.util.PythonInterpreter.<init>(PythonInterpreter.java:67)
>at
>org.Python.util.PythonInterpreter.<init>(PythonInterpreter.java:45)
>at PyFactory.initialize(PyFactory.java 9)
>at A.run(A.java 9)
>
>The classes I am using are as follows(I have included
>only the required portion of the code):-

[A very good example snipped. This kind of bugs can be hell to track
down, but with your example it was very easy. Thanks]

>Pl explain the cause of the error. When I am creating
>and running only one thread then it works fine. But
>with more than one threads, it gives this exception.

As you have probably guessed, it is a synchronization bug in jython and
we will ofcourse add a fix to jython. Meanwhile you can change the
definition of your own PyFactory.initialize() to:

  public static synchronized void initialize() 
         throws ClassNotFoundException{
    pyInterp=new PythonInterpreter();
  }

as a workaround.

regards,
finn