return new FilteredSortedSet<>(((SortedSet<E>) unfiltered).headSet(toElement), predicate);
    }

    @Override
    public SortedSet<E> tailSet(@ParametricNullness E fromElement) {
      return new FilteredSortedSet<>(((SortedSet<E>) unfiltered).tailSet(fromElement), predicate);
    }

    @Override
    @ParametricNullness
    public E first() {

    }

    @Override
    public NavigableSet<E> tailSet(E fromElement, boolean inclusive) {
      synchronized (mutex) {
        return Synchronized.navigableSet(delegate().tailSet(fromElement, inclusive), mutex);
      }
    }

    @Override
    public SortedSet<E> tailSet(E fromElement) {
      return tailSet(fromElement, true);
    }

    }

    @Override
    public NavigableSet<E> tailSet(E fromElement, boolean inclusive) {
      synchronized (mutex) {
        return Synchronized.navigableSet(delegate().tailSet(fromElement, inclusive), mutex);
      }
    }

    @Override
    public SortedSet<E> tailSet(E fromElement) {
      return tailSet(fromElement, true);
    }

synagogue:before{content:"\f69b"}.fa-sync:before{content:"\f021"}.fa-sync-alt:before{content:"\f2f1"}.fa-syringe:before{content:"\f48e"}.fa-table:before{content:"\f0ce"}.fa-table-tennis:before{content:"\f45d"}.fa-tablet:before{content:"\f10a"}.fa-tablet-alt:before{content:"\f3fa"}.fa-tablets:before{content:"\f490"}.fa-tachometer-alt:before{content:"\f3fd"}.fa-tag:before{content:"\f02b"}.fa-tags:before{content:"\f02c"}.fa-tape:before{content:"\f4db"}.fa-tasks:before{content:"\f0ae"}.fa-taxi:befor...

synagogue:before{content:"\f69b"}.fa-sync:before{content:"\f021"}.fa-sync-alt:before{content:"\f2f1"}.fa-syringe:before{content:"\f48e"}.fa-table:before{content:"\f0ce"}.fa-table-tennis:before{content:"\f45d"}.fa-tablet:before{content:"\f10a"}.fa-tablet-alt:before{content:"\f3fa"}.fa-tablets:before{content:"\f490"}.fa-tachometer-alt:before{content:"\f3fd"}.fa-tag:before{content:"\f02b"}.fa-tags:before{content:"\f02c"}.fa-tape:before{content:"\f4db"}.fa-tasks:before{content:"\f0ae"}.fa-taxi:befor...