public RString restartGroup ( String what ) { List < Placeholder > all = _placeholders . get ( what ) ; assert all . size ( ) == 1 ; Placeholder result = all . get ( 0 ) ; if ( result . group == null ) { throw new NoSuchElementException ( "Element " + what + " is not a group." ) ; } result . group . clear ( ) ; return result . group ; }
can be filled again .