return the first not null value , or null if both are null . defined for el as ` object firstnotnull object , object ' . concode_field_sep int SUBMIT_MINUTES concode_elem_sep long KB concode_elem_sep long MB concode_elem_sep int SUBMIT_DAYS concode_elem_sep int SUBMIT_HOURS concode_elem_sep long PB concode_elem_sep long TB concode_elem_sep long GB concode_field_sep String trim concode_elem_sep String concat concode_elem_sep String urlEncode concode_elem_sep String timestamp