public MutableSortedSet<T> toSortedSet(Comparator<? super T> comparator) {
   return TreeSortedSet.newSet(comparator, this);
 }
 @Test
 public void toSortedSetBy() {
   ImmutableCollection<Integer> integers = this.classUnderTest();
   MutableSortedSet<Integer> set = integers.toSortedSetBy(Functions.getToString());
   Verify.assertSortedSetsEqual(TreeSortedSet.newSet(integers), set);
 }
 public MutableSortedSet<T> toSortedSet() {
   return TreeSortedSet.newSet(null, this);
 }
 public PartitionTreeSortedSet(Comparator<? super T> comparator, Predicate<? super T> predicate) {
   super(predicate);
   this.selected = TreeSortedSet.newSet(comparator);
   this.rejected = TreeSortedSet.newSet(comparator);
 }