code: public void setMapOutputValueClass(Class<?> theClass
                                       ) throws IllegalStateException {
      ensureState(JobState.DEFINE);
      conf.setMapOutputValueClass(theClass);
    }
docs: Set the value class for the map output data. This allows the user to
  specify the map output value class to be different than the final output
  value class.
  
  @param theClass the map output value class.
  @throws IllegalStateException if the job is submitted