How to return null param from a stored procedure?

[Jeremy Boynes]

I have a stored procedure where I want to return a null value from one 
its parameters - something like:

    public static void Int_Proc2(Integer[] param) {
        param[0] = null;
    }
I am declaring this to Derby as:
  CREATE PROCEDURE Int_Proc2(OUT param INTEGER)
  PARAMETER STYLE JAVA
  LANGUAGE JAVA
  READS SQL DATA
  EXTERNAL NAME 'test.jdbc.CallableStatementTest.Int_Proc2'
but a prepareCall("{call Int_Proc2(?)}");
throws a 42X50 SQLException (no method found ...)
Using a primitive int works fine but obviously I can't return null that 
way. How should I be doing this?

Thanks
--
Jeremy