public TreeSet() 
{
        this(new TreeMap< E,Object >());
}

Constructs a new, empty tree set, sorted according to the natural ordering of its elements. All elements inserted into the set must implement the Comparable interface. Furthermore, all such elements must be mutually comparable: {@code e1.compareTo(e2)} must not throw a {@code ClassCastException} for any elements {@code e1} and {@code e2} in the set. If the user attempts to add an element to the set that violates this constraint (for example, the user attempts to add a string element to a set whose elements are integers), the {@code add} call will throw a {@code ClassCastException}.

 TreeSet(NavigableMap<E, Object> m) 
{
        this.m = m;
}

Constructs a set backed by the specified navigable map.

 public TreeSet(Comparator<? super E> comparator) 
{
        this(new TreeMap<  >(comparator));
}

Constructs a new, empty tree set, sorted according to the specified comparator. All elements inserted into the set must be mutually comparable by the specified comparator: {@code comparator.compare(e1, e2)} must not throw a {@code ClassCastException} for any elements {@code e1} and {@code e2} in the set. If the user attempts to add an element to the set that violates this constraint, the {@code add} call will throw a {@code ClassCastException}.

Parameters:

comparator - the comparator that will be used to order this set. If {@code null}, the {@linkplain Comparable natural ordering} of the elements will be used.

 public TreeSet(Collection<? extends E> c) 
{
        this();
        addAll(c);
}

Constructs a new tree set containing the elements in the specified collection, sorted according to the natural ordering of its elements. All elements inserted into the set must implement the Comparable interface. Furthermore, all such elements must be mutually comparable: {@code e1.compareTo(e2)} must not throw a {@code ClassCastException} for any elements {@code e1} and {@code e2} in the set.

Parameters:

c - collection whose elements will comprise the new set

Throws:

ClassCastException - if the elements in {@code c} are not Comparable , or are not mutually comparable

NullPointerException - if the specified collection is null

 public TreeSet(SortedSet<E> s) 
{
        this(s.comparator());
        addAll(s);
}

Constructs a new tree set containing the same elements and using the same ordering as the specified sorted set.

Parameters:

s - sorted set whose elements will comprise the new set

Throws:

NullPointerException - if the specified sorted set is null

 public boolean add(E e) 
{
        return m.put(e, PRESENT)==null;
}

Adds the specified element to this set if it is not already present. More formally, adds the specified element {@code e} to this set if the set contains no element {@code e2} such that (e==null ? e2==null : e.equals(e2)). If this set already contains the element, the call leaves the set unchanged and returns {@code false}.

 public boolean addAll(Collection<? extends E> c) 
{
        // Use linear-time version if applicable
        if (m.size()==0 && c.size()  > 0 &&
            c instanceof SortedSet &&
            m instanceof TreeMap) {
            SortedSet< ? extends E > set = (SortedSet< ? extends E >) c;
            TreeMap< E,Object > map = (TreeMap< E, Object >) m;
            Comparator< ? super E > cc = (Comparator< ? super E >) set.comparator();
            Comparator< ? super E > mc = map.comparator();
            if (cc==mc || (cc != null && cc.equals(mc))) {
                map.addAllForTreeSet(set, PRESENT);
                return true;
            }
        }
        return super.addAll(c);
}

Adds all of the elements in the specified collection to this set.

 public E ceiling(E e) 
{
        return m.ceilingKey(e);
}

 public  void clear() 
{
        m.clear();
}

Removes all of the elements from this set. The set will be empty after this call returns.

 public Object clone() 
{
        TreeSet< E > clone = null;
        try {
            clone = (TreeSet< E >) super.clone();
        } catch (CloneNotSupportedException e) {
            throw new InternalError();
        }
        clone.m = new TreeMap<  >(m);
        return clone;
}

Returns a shallow copy of this {@code TreeSet} instance. (The elements themselves are not cloned.)

 public Comparator<? super E> comparator() 
{
        return m.comparator();
}

 public boolean contains(Object o) 
{
        return m.containsKey(o);
}

Returns {@code true} if this set contains the specified element. More formally, returns {@code true} if and only if this set contains an element {@code e} such that (o==null ? e==null : o.equals(e)).

 public Iterator<E> descendingIterator() 
{
        return m.descendingKeySet().iterator();
}

Returns an iterator over the elements in this set in descending order.

 public NavigableSet<E> descendingSet() 
{
        return new TreeSet<  >(m.descendingMap());
}

 public E first() 
{
        return m.firstKey();
}

 public E floor(E e) 
{
        return m.floorKey(e);
}

 public SortedSet<E> headSet(E toElement) 
{
        return headSet(toElement, false);
}

 public NavigableSet<E> headSet(E toElement,
    boolean inclusive) 
{
        return new TreeSet<  >(m.headMap(toElement, inclusive));
}

 public E higher(E e) 
{
        return m.higherKey(e);
}

 public boolean isEmpty() 
{
        return m.isEmpty();
}

Returns {@code true} if this set contains no elements.

 public Iterator<E> iterator() 
{
        return m.navigableKeySet().iterator();
}

Returns an iterator over the elements in this set in ascending order.

 public E last() 
{
        return m.lastKey();
}

 public E lower(E e) 
{
        return m.lowerKey(e);
}

 public E pollFirst() 
{
        Map.Entry< E,? > e = m.pollFirstEntry();
        return (e == null) ? null : e.getKey();
}

 public E pollLast() 
{
        Map.Entry< E,? > e = m.pollLastEntry();
        return (e == null) ? null : e.getKey();
}

 public boolean remove(Object o) 
{
        return m.remove(o)==PRESENT;
}

Removes the specified element from this set if it is present. More formally, removes an element {@code e} such that (o==null ? e==null : o.equals(e)), if this set contains such an element. Returns {@code true} if this set contained the element (or equivalently, if this set changed as a result of the call). (This set will not contain the element once the call returns.)

 public int size() 
{
        return m.size();
}

Returns the number of elements in this set (its cardinality).

 public SortedSet<E> subSet(E fromElement,
    E toElement) 
{
        return subSet(fromElement, true, toElement, false);
}

 public NavigableSet<E> subSet(E fromElement,
    boolean fromInclusive,
    E toElement,
    boolean toInclusive) 
{
        return new TreeSet<  >(m.subMap(fromElement, fromInclusive,
                                       toElement,   toInclusive));
}

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

 public NavigableSet<E> tailSet(E fromElement,
    boolean inclusive) 
{
        return new TreeSet<  >(m.tailMap(fromElement, inclusive));
}