create a callable that always returns null . concode_field_sep Runnable m_aRunnable concode_elem_sep DATATYPE m_aResult concode_field_sep DATATYPE call concode_elem_sep String toString
AdapterRunnableToCallable < Object > function ( @ Nonnull final Runnable arg0 ) { return new AdapterRunnableToCallable < Object > ( arg0 ) ; }