private boolean removeIf(Predicate<Tombstone> predicate){
  return removeUnexpiredIf(predicate) || removeExpiredIf(predicate);
}

private boolean removeIf ( Predicate < Tombstone > predicate ) { return removeUnexpiredIf ( predicate ) || removeExpiredIf ( predicate ) ; }
for all tombstone this sweeper knows about call the predicate . if the predicate returns true then remove the tombstone from any storage and update the memory estimate .
