return TreeSortedSet.newSet(this.comparator());
    }
    public ImmutableBooleanList collectBoolean(BooleanFunction<? super T> booleanFunction)
    {
        BooleanArrayList result = new BooleanArrayList(this.size());
        this.forEach(new CollectBooleanProcedure<T>(booleanFunction, result));
        return result.toImmutable();
    }