java/util/TreeSet.java

/*
 * %W% %E%
 *
 * Copyright 2006 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

package java.util;

/**
 * A {@link NavigableSet} implementation based on a {@link TreeMap}.
 * The elements are ordered using their {@linkplain Comparable natural
 * ordering}, or by a {@link Comparator} provided at set creation
 * time, depending on which constructor is used.
 *
 * <p>This implementation provides guaranteed log(n) time cost for the basic
 * operations ({@code add}, {@code remove} and {@code contains}).
 *
 * <p>Note that the ordering maintained by a set (whether or not an explicit
 * comparator is provided) must be <i>consistent with equals</i> if it is to
 * correctly implement the {@code Set} interface.  (See {@code Comparable}
 * or {@code Comparator} for a precise definition of <i>consistent with
 * equals</i>.)  This is so because the {@code Set} interface is defined in
 * terms of the {@code equals} operation, but a {@code TreeSet} instance
 * performs all element comparisons using its {@code compareTo} (or
 * {@code compare}) method, so two elements that are deemed equal by this method
 * are, from the standpoint of the set, equal.  The behavior of a set
 * <i>is</i> well-defined even if its ordering is inconsistent with equals; it
 * just fails to obey the general contract of the {@code Set} interface.
 *
 * <p><strong>Note that this implementation is not synchronized.</strong>
 * If multiple threads access a tree set concurrently, and at least one
 * of the threads modifies the set, it <i>must</i> be synchronized
 * externally.  This is typically accomplished by synchronizing on some
 * object that naturally encapsulates the set.
 * If no such object exists, the set should be "wrapped" using the
 * {@link Collections#synchronizedSortedSet Collections.synchronizedSortedSet}
 * method.  This is best done at creation time, to prevent accidental
 * unsynchronized access to the set: <pre>
 *   SortedSet s = Collections.synchronizedSortedSet(new TreeSet(...));</pre>
 *
 * <p>The iterators returned by this class's {@code iterator} method are
 * <i>fail-fast</i>: if the set is modified at any time after the iterator is
 * created, in any way except through the iterator's own {@code remove}
 * method, the iterator will throw a {@link ConcurrentModificationException}.
 * Thus, in the face of concurrent modification, the iterator fails quickly
 * and cleanly, rather than risking arbitrary, non-deterministic behavior at
 * an undetermined time in the future.
 *
 * <p>Note that the fail-fast behavior of an iterator cannot be guaranteed
 * as it is, generally speaking, impossible to make any hard guarantees in the
 * presence of unsynchronized concurrent modification.  Fail-fast iterators
 * throw {@code ConcurrentModificationException} on a best-effort basis.
 * Therefore, it would be wrong to write a program that depended on this
 * exception for its correctness:   <i>the fail-fast behavior of iterators
 * should be used only to detect bugs.</i>
 *
 * <p>This class is a member of the
 * <a href="{@docRoot}/../guide/collections/index.html">
 * Java Collections Framework</a>.
 *
 * @param <E> the type of elements maintained by this set
 *
 * @author  Josh Bloch
 * @version %I%, %G%
 * @see     Collection
 * @see     Set
 * @see     HashSet
 * @see     Comparable
 * @see     Comparator
 * @see     TreeMap
 * @since   1.2
 */

public class TreeSet<E> extends AbstractSet<E>
    implements NavigableSet<E>, Cloneable, java.io.Serializable
{
    /** 
     * The backing map.
     */
    private transient NavigableMap<E,Object> m; 

    // Dummy value to associate with an Object in the backing Map
    private static final Object PRESENT = new Object();

    /**
     * Constructs a set backed by the specified navigable map.
     */
    TreeSet(NavigableMap<E,Object> m) {
        this.m = m;
    }

    /**
     * Constructs a new, empty tree set, sorted according to the
     * natural ordering of its elements.  All elements inserted into
     * the set must implement the {@link Comparable} interface.
     * Furthermore, all such elements must be <i>mutually
     * comparable</i>: {@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(Object)} call will throw a
     * {@code ClassCastException}.
     */
    public TreeSet() {
        this(new TreeMap<E,Object>());
    }

    /**
     * Constructs a new, empty tree set, sorted according to the specified
     * comparator.  All elements inserted into the set must be <i>mutually
     * comparable</i> 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(Object)} call will throw a {@code ClassCastException}.
     *
     * @param 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(Comparator<? super E> comparator) {
        this(new TreeMap<E,Object>(comparator));
    }

    /**
     * Constructs a new tree set containing the elements in the specified
     * collection, sorted according to the <i>natural ordering</i> of its
     * elements.  All elements inserted into the set must implement the
     * {@link Comparable} interface.  Furthermore, all such elements must be
     * <i>mutually comparable</i>: {@code e1.compareTo(e2)} must not throw a
     * {@code ClassCastException} for any elements {@code e1} and
     * {@code e2} in the set.
     *
     * @param c collection whose elements will comprise the new set
     * @throws ClassCastException if the elements in {@code c} are
     *         not {@link Comparable}, or are not mutually comparable
     * @throws NullPointerException if the specified collection is null
     */
    public TreeSet(Collection<? extends E> c) {
        this();
        addAll(c);
    }

    /**
     * Constructs a new tree set containing the same elements and
     * using the same ordering as the specified sorted set.
     *
     * @param s sorted set whose elements will comprise the new set
     * @throws NullPointerException if the specified sorted set is null
     */
    public TreeSet(SortedSet<E> s) {
        this(s.comparator());
        addAll(s);
    }

    /**
     * Returns an iterator over the elements in this set in ascending order.
     *
     * @return an iterator over the elements in this set in ascending order
     */
    public Iterator<E> iterator() {
        return m.navigableKeySet().iterator();
    }

    /**
     * Returns an iterator over the elements in this set in descending order.
     *
     * @return an iterator over the elements in this set in descending order
     * @since 1.6
     */
    public Iterator<E> descendingIterator() {
        return m.descendingKeySet().iterator();
    }

    /**
     * @since 1.6
     */
    public NavigableSet<E> descendingSet() {
        return new TreeSet(m.descendingMap());
    }

    /**
     * Returns the number of elements in this set (its cardinality).
     *
     * @return the number of elements in this set (its cardinality)
     */
    public int size() {
        return m.size();
    }

    /**
     * Returns {@code true} if this set contains no elements.
     *
     * @return {@code true} if this set contains no elements
     */
    public boolean isEmpty() {
        return m.isEmpty();
    }

    /**
     * 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
     * {@code (o==null&nbsp;?&nbsp;e==null&nbsp;:&nbsp;o.equals(e))}.
     *
     * @param o object to be checked for containment in this set
     * @return {@code true} if this set contains the specified element
     * @throws ClassCastException if the specified object cannot be compared
     *         with the elements currently in the set
     * @throws NullPointerException if the specified element is null
     *         and this set uses natural ordering, or its comparator
     *         does not permit null elements
     */
    public boolean contains(Object o) {
        return m.containsKey(o);
    }

    /**
     * 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
     * {@code (e==null&nbsp;?&nbsp;e2==null&nbsp;:&nbsp;e.equals(e2))}.
     * If this set already contains the element, the call leaves the set
     * unchanged and returns {@code false}.
     *
     * @param e element to be added to this set
     * @return {@code true} if this set did not already contain the specified
     *         element
     * @throws ClassCastException if the specified object cannot be compared
     *         with the elements currently in this set
     * @throws NullPointerException if the specified element is null
     *         and this set uses natural ordering, or its comparator
     *         does not permit null elements
     */
    public boolean add(E e) {
        return m.put(e, PRESENT)==null;
    }

    /**
     * Removes the specified element from this set if it is present.
     * More formally, removes an element {@code e} such that
     * {@code (o==null&nbsp;?&nbsp;e==null&nbsp;:&nbsp;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.)
     *
     * @param o object to be removed from this set, if present
     * @return {@code true} if this set contained the specified element
     * @throws ClassCastException if the specified object cannot be compared
     *         with the elements currently in this set
     * @throws NullPointerException if the specified element is null
     *         and this set uses natural ordering, or its comparator
     *         does not permit null elements
     */
    public boolean remove(Object o) {
        return m.remove(o)==PRESENT;
    }

    /**
     * Removes all of the elements from this set.
     * The set will be empty after this call returns.
     */
    public void clear() {
        m.clear();
    }

    /**
     * Adds all of the elements in the specified collection to this set.
     *
     * @param c collection containing elements to be added to this set
     * @return {@code true} if this set changed as a result of the call
     * @throws ClassCastException if the elements provided cannot be compared
     *         with the elements currently in the set
     * @throws NullPointerException if the specified collection is null or
     *         if any element is null and this set uses natural ordering, or
     *         its comparator does not permit null elements
     */
    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);
    }

    /**
     * @throws ClassCastException {@inheritDoc}
     * @throws NullPointerException if {@code fromElement} or {@code toElement}
     *         is null and this set uses natural ordering, or its comparator
     *         does not permit null elements
     * @throws IllegalArgumentException {@inheritDoc}
     * @since 1.6
     */
    public NavigableSet<E> navigableSubSet(E fromElement, boolean fromInclusive,
                                           E toElement,   boolean toInclusive) {
        return new TreeSet<E>(m.navigableSubMap(fromElement, fromInclusive,
                                                toElement,   toInclusive));
    }

    /**
     * @throws ClassCastException {@inheritDoc}
     * @throws NullPointerException if {@code toElement} is null and
     *         this set uses natural ordering, or its comparator does
     *         not permit null elements
     * @throws IllegalArgumentException {@inheritDoc}
     * @since 1.6
     */
    public NavigableSet<E> navigableHeadSet(E toElement, boolean inclusive) {
        return new TreeSet<E>(m.navigableHeadMap(toElement, inclusive));
    }

    /**
     * @throws ClassCastException {@inheritDoc}
     * @throws NullPointerException if {@code fromElement} is null and
     *         this set uses natural ordering, or its comparator does
     *         not permit null elements
     * @throws IllegalArgumentException {@inheritDoc}
     * @since 1.6
     */
    public NavigableSet<E> navigableTailSet(E fromElement, boolean inclusive) {
        return new TreeSet<E>(m.navigableTailMap(fromElement, inclusive));
    }

    /**
     * @throws ClassCastException {@inheritDoc}
     * @throws NullPointerException if {@code fromElement} or
     *         {@code toElement} is null and this set uses natural ordering,
     *         or its comparator does not permit null elements
     * @throws IllegalArgumentException {@inheritDoc}
     */
    public SortedSet<E> subSet(E fromElement, E toElement) {
        return navigableSubSet(fromElement, true, toElement, false);
    }

    /**
     * @throws ClassCastException {@inheritDoc}
     * @throws NullPointerException if {@code toElement} is null
     *         and this set uses natural ordering, or its comparator does
     *         not permit null elements
     * @throws IllegalArgumentException {@inheritDoc}
     */
    public SortedSet<E> headSet(E toElement) {
        return navigableHeadSet(toElement, false);
    }

    /**
     * @throws ClassCastException {@inheritDoc}
     * @throws NullPointerException if {@code fromElement} is null
     *         and this set uses natural ordering, or its comparator does
     *         not permit null elements
     * @throws IllegalArgumentException {@inheritDoc}
     */
    public SortedSet<E> tailSet(E fromElement) {
        return navigableTailSet(fromElement, true);
    }

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

    /**
     * @throws NoSuchElementException {@inheritDoc}
     */
    public E first() {
        return m.firstKey();
    }

    /**
     * @throws NoSuchElementException {@inheritDoc}
     */
    public E last() {
        return m.lastKey();
    }

    // NavigableSet API methods

    /**
     * @throws ClassCastException {@inheritDoc}
     * @throws NullPointerException if the specified element is null
     *         and this set uses natural ordering, or its comparator
     *         does not permit null elements
     * @since 1.6
     */
    public E lower(E e) {
        return m.lowerKey(e);
    }

    /**
     * @throws ClassCastException {@inheritDoc}
     * @throws NullPointerException if the specified element is null
     *         and this set uses natural ordering, or its comparator
     *         does not permit null elements
     * @since 1.6
     */
    public E floor(E e) {
        return m.floorKey(e);
    }

    /**
     * @throws ClassCastException {@inheritDoc}
     * @throws NullPointerException if the specified element is null
     *         and this set uses natural ordering, or its comparator
     *         does not permit null elements
     * @since 1.6
     */
    public E ceiling(E e) {
        return m.ceilingKey(e);
    }

    /**
     * @throws ClassCastException {@inheritDoc}
     * @throws NullPointerException if the specified element is null
     *         and this set uses natural ordering, or its comparator
     *         does not permit null elements
     * @since 1.6
     */
    public E higher(E e) {
        return m.higherKey(e);
    }

    /**
     * @since 1.6
     */
    public E pollFirst() {
        Map.Entry<E,?> e = m.pollFirstEntry();
        return (e == null)? null : e.getKey();
    }

    /**
     * @since 1.6
     */
    public E pollLast() {
        Map.Entry<E,?> e = m.pollLastEntry();
        return (e == null)? null : e.getKey();
    }

    /**
     * Returns a shallow copy of this {@code TreeSet} instance. (The elements
     * themselves are not cloned.)
     *
     * @return a shallow copy of this set
     */
    public Object clone() {
        TreeSet<E> clone = null;
        try {
            clone = (TreeSet<E>) super.clone();
        } catch (CloneNotSupportedException e) {
            throw new InternalError();
        }

        clone.m = new TreeMap<E,Object>(m);
        return clone;
    }

    /**
     * Save the state of the {@code TreeSet} instance to a stream (that is,
     * serialize it).
     *
     * @serialData Emits the comparator used to order this set, or
     *             {@code null} if it obeys its elements' natural ordering
     *             (Object), followed by the size of the set (the number of
     *             elements it contains) (int), followed by all of its
     *             elements (each an Object) in order (as determined by the
     *             set's Comparator, or by the elements' natural ordering if
     *             the set has no Comparator).
     */
    private void writeObject(java.io.ObjectOutputStream s)
        throws java.io.IOException {
        // Write out any hidden stuff
        s.defaultWriteObject();

        // Write out Comparator
        s.writeObject(m.comparator());

        // Write out size
        s.writeInt(m.size());

        // Write out all elements in the proper order.
        for (Iterator i=m.keySet().iterator(); i.hasNext(); )
            s.writeObject(i.next());
    }

    /**
     * Reconstitute the {@code TreeSet} instance from a stream (that is,
     * deserialize it).
     */
    private void readObject(java.io.ObjectInputStream s)
        throws java.io.IOException, ClassNotFoundException {
        // Read in any hidden stuff
        s.defaultReadObject();

        // Read in Comparator
        Comparator<? super E> c = (Comparator<? super E>) s.readObject();

        // Create backing TreeMap
        TreeMap<E,Object> tm;
        if (c==null)
            tm = new TreeMap<E,Object>();
        else
            tm = new TreeMap<E,Object>(c);
        m = tm;

        // Read in size
        int size = s.readInt();

        tm.readTreeSet(size, s, PRESENT);
    }

    private static final long serialVersionUID = -2479143000061671589L;
}
Revision:	1.21
Committed:	Wed Apr 19 15:07:14 2006 UTC (18 years, 1 month ago) by dl
Branch:	MAIN
Changes since 1.20:	+80 -85 lines
Log Message:	Updated Navigable interfaces ind implementations
#	User	Rev	Content
1	dl	1.1	/*
2			* %W% %E%
3			*
4	jsr166	1.19	* Copyright 2006 Sun Microsystems, Inc. All rights reserved.
5	dl	1.1	* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
6			*/
7
8	jsr166	1.8	package java.util;
9	dl	1.1
10			/**
11	jsr166	1.11	* A {@link NavigableSet} implementation based on a {@link TreeMap}.
12			* The elements are ordered using their {@linkplain Comparable natural
13			* ordering}, or by a {@link Comparator} provided at set creation
14			* time, depending on which constructor is used.
15	dl	1.1	*
16	jsr166	1.11	* <p>This implementation provides guaranteed log(n) time cost for the basic
17	dl	1.21	* operations ({@code add}, {@code remove} and {@code contains}).
18	dl	1.1	*
19	jsr166	1.11	* <p>Note that the ordering maintained by a set (whether or not an explicit
20	dl	1.1	* comparator is provided) must be <i>consistent with equals</i> if it is to
21	dl	1.21	* correctly implement the {@code Set} interface. (See {@code Comparable}
22			* or {@code Comparator} for a precise definition of <i>consistent with
23			* equals</i>.) This is so because the {@code Set} interface is defined in
24			* terms of the {@code equals} operation, but a {@code TreeSet} instance
25			* performs all element comparisons using its {@code compareTo} (or
26			* {@code compare}) method, so two elements that are deemed equal by this method
27	dl	1.1	* are, from the standpoint of the set, equal. The behavior of a set
28			* <i>is</i> well-defined even if its ordering is inconsistent with equals; it
29	dl	1.21	* just fails to obey the general contract of the {@code Set} interface.
30	dl	1.1	*
31	jsr166	1.18	* <p><strong>Note that this implementation is not synchronized.</strong>
32			* If multiple threads access a tree set concurrently, and at least one
33			* of the threads modifies the set, it <i>must</i> be synchronized
34			* externally. This is typically accomplished by synchronizing on some
35			* object that naturally encapsulates the set.
36			* If no such object exists, the set should be "wrapped" using the
37			* {@link Collections#synchronizedSortedSet Collections.synchronizedSortedSet}
38			* method. This is best done at creation time, to prevent accidental
39			* unsynchronized access to the set: <pre>
40			* SortedSet s = Collections.synchronizedSortedSet(new TreeSet(...));</pre>
41	dl	1.1	*
42	dl	1.21	* <p>The iterators returned by this class's {@code iterator} method are
43	dl	1.1	* <i>fail-fast</i>: if the set is modified at any time after the iterator is
44	dl	1.21	* created, in any way except through the iterator's own {@code remove}
45	jsr166	1.11	* method, the iterator will throw a {@link ConcurrentModificationException}.
46	dl	1.1	* Thus, in the face of concurrent modification, the iterator fails quickly
47			* and cleanly, rather than risking arbitrary, non-deterministic behavior at
48			* an undetermined time in the future.
49			*
50			* <p>Note that the fail-fast behavior of an iterator cannot be guaranteed
51			* as it is, generally speaking, impossible to make any hard guarantees in the
52			* presence of unsynchronized concurrent modification. Fail-fast iterators
53	dl	1.21	* throw {@code ConcurrentModificationException} on a best-effort basis.
54	dl	1.1	* Therefore, it would be wrong to write a program that depended on this
55			* exception for its correctness: <i>the fail-fast behavior of iterators
56	jsr166	1.10	* should be used only to detect bugs.</i>
57	dl	1.1	*
58	jsr166	1.10	* <p>This class is a member of the
59	dl	1.1	* <a href="{@docRoot}/../guide/collections/index.html">
60			* Java Collections Framework</a>.
61			*
62	jsr166	1.11	* @param <E> the type of elements maintained by this set
63			*
64	dl	1.1	* @author Josh Bloch
65			* @version %I%, %G%
66			* @see Collection
67			* @see Set
68			* @see HashSet
69			* @see Comparable
70			* @see Comparator
71			* @see TreeMap
72			* @since 1.2
73			*/
74
75	dl	1.21	public class TreeSet<E> extends AbstractSet<E>
76	dl	1.1	implements NavigableSet<E>, Cloneable, java.io.Serializable
77			{
78	dl	1.21	/**
79			* The backing map.
80			*/
81			private transient NavigableMap<E,Object> m;
82	dl	1.1
83			// Dummy value to associate with an Object in the backing Map
84			private static final Object PRESENT = new Object();
85
86			/**
87	jsr166	1.11	* Constructs a set backed by the specified navigable map.
88	dl	1.1	*/
89	dl	1.21	TreeSet(NavigableMap<E,Object> m) {
90	dl	1.1	this.m = m;
91			}
92
93			/**
94	jsr166	1.11	* Constructs a new, empty tree set, sorted according to the
95			* natural ordering of its elements. All elements inserted into
96			* the set must implement the {@link Comparable} interface.
97			* Furthermore, all such elements must be <i>mutually
98	dl	1.21	* comparable</i>: {@code e1.compareTo(e2)} must not throw a
99			* {@code ClassCastException} for any elements {@code e1} and
100			* {@code e2} in the set. If the user attempts to add an element
101	jsr166	1.11	* to the set that violates this constraint (for example, the user
102			* attempts to add a string element to a set whose elements are
103	dl	1.21	* integers), the {@code add(Object)} call will throw a
104			* {@code ClassCastException}.
105	dl	1.1	*/
106			public TreeSet() {
107			this(new TreeMap<E,Object>());
108			}
109
110			/**
111	jsr166	1.12	* Constructs a new, empty tree set, sorted according to the specified
112			* comparator. All elements inserted into the set must be <i>mutually
113	dl	1.21	* comparable</i> by the specified comparator: {@code comparator.compare(e1,
114			* e2)} must not throw a {@code ClassCastException} for any elements
115			* {@code e1} and {@code e2} in the set. If the user attempts to add
116	jsr166	1.12	* an element to the set that violates this constraint, the
117	dl	1.21	* {@code add(Object)} call will throw a {@code ClassCastException}.
118	jsr166	1.11	*
119			* @param comparator the comparator that will be used to order this set.
120	dl	1.21	* If {@code null}, the {@linkplain Comparable natural
121	jsr166	1.11	* ordering} of the elements will be used.
122			*/
123			public TreeSet(Comparator<? super E> comparator) {
124			this(new TreeMap<E,Object>(comparator));
125	dl	1.1	}
126
127			/**
128	jsr166	1.12	* Constructs a new tree set containing the elements in the specified
129			* collection, sorted according to the <i>natural ordering</i> of its
130			* elements. All elements inserted into the set must implement the
131			* {@link Comparable} interface. Furthermore, all such elements must be
132	dl	1.21	* <i>mutually comparable</i>: {@code e1.compareTo(e2)} must not throw a
133			* {@code ClassCastException} for any elements {@code e1} and
134			* {@code e2} in the set.
135	jsr166	1.11	*
136			* @param c collection whose elements will comprise the new set
137	dl	1.21	* @throws ClassCastException if the elements in {@code c} are
138	jsr166	1.11	* not {@link Comparable}, or are not mutually comparable
139			* @throws NullPointerException if the specified collection is null
140	dl	1.1	*/
141			public TreeSet(Collection<? extends E> c) {
142			this();
143			addAll(c);
144			}
145
146			/**
147	jsr166	1.11	* Constructs a new tree set containing the same elements and
148			* using the same ordering as the specified sorted set.
149	dl	1.1	*
150	jsr166	1.11	* @param s sorted set whose elements will comprise the new set
151			* @throws NullPointerException if the specified sorted set is null
152	dl	1.1	*/
153			public TreeSet(SortedSet<E> s) {
154			this(s.comparator());
155			addAll(s);
156			}
157
158			/**
159	jsr166	1.13	* Returns an iterator over the elements in this set in ascending order.
160	dl	1.1	*
161	jsr166	1.13	* @return an iterator over the elements in this set in ascending order
162	dl	1.1	*/
163			public Iterator<E> iterator() {
164	dl	1.21	return m.navigableKeySet().iterator();
165	dl	1.1	}
166
167			/**
168	jsr166	1.13	* Returns an iterator over the elements in this set in descending order.
169	dl	1.1	*
170	jsr166	1.13	* @return an iterator over the elements in this set in descending order
171	jsr166	1.17	* @since 1.6
172	dl	1.1	*/
173			public Iterator<E> descendingIterator() {
174			return m.descendingKeySet().iterator();
175			}
176
177			/**
178	dl	1.21	* @since 1.6
179			*/
180			public NavigableSet<E> descendingSet() {
181			return new TreeSet(m.descendingMap());
182			}
183
184			/**
185	dl	1.1	* Returns the number of elements in this set (its cardinality).
186			*
187	jsr166	1.11	* @return the number of elements in this set (its cardinality)
188	dl	1.1	*/
189			public int size() {
190			return m.size();
191			}
192
193			/**
194	dl	1.21	* Returns {@code true} if this set contains no elements.
195	dl	1.1	*
196	dl	1.21	* @return {@code true} if this set contains no elements
197	dl	1.1	*/
198			public boolean isEmpty() {
199			return m.isEmpty();
200			}
201
202			/**
203	dl	1.21	* Returns {@code true} if this set contains the specified element.
204			* More formally, returns {@code true} if and only if this set
205			* contains an element {@code e} such that
206			* {@code (o==null ? e==null : o.equals(e))}.
207	dl	1.1	*
208	jsr166	1.16	* @param o object to be checked for containment in this set
209	dl	1.21	* @return {@code true} if this set contains the specified element
210	dl	1.1	* @throws ClassCastException if the specified object cannot be compared
211	jsr166	1.11	* with the elements currently in the set
212	jsr166	1.15	* @throws NullPointerException if the specified element is null
213			* and this set uses natural ordering, or its comparator
214			* does not permit null elements
215	dl	1.1	*/
216			public boolean contains(Object o) {
217			return m.containsKey(o);
218			}
219
220			/**
221			* Adds the specified element to this set if it is not already present.
222	dl	1.21	* More formally, adds the specified element {@code e} to this set if
223			* the set contains no element {@code e2} such that
224			* {@code (e==null ? e2==null : e.equals(e2))}.
225	jsr166	1.16	* If this set already contains the element, the call leaves the set
226	dl	1.21	* unchanged and returns {@code false}.
227	dl	1.1	*
228	jsr166	1.11	* @param e element to be added to this set
229	dl	1.21	* @return {@code true} if this set did not already contain the specified
230	jsr166	1.11	* element
231	dl	1.1	* @throws ClassCastException if the specified object cannot be compared
232	jsr166	1.16	* with the elements currently in this set
233	jsr166	1.15	* @throws NullPointerException if the specified element is null
234			* and this set uses natural ordering, or its comparator
235			* does not permit null elements
236	dl	1.1	*/
237	jsr166	1.7	public boolean add(E e) {
238			return m.put(e, PRESENT)==null;
239	dl	1.1	}
240
241			/**
242			* Removes the specified element from this set if it is present.
243	dl	1.21	* More formally, removes an element {@code e} such that
244			* {@code (o==null ? e==null : o.equals(e))},
245			* if this set contains such an element. Returns {@code true} if
246	jsr166	1.16	* this set contained the element (or equivalently, if this set
247			* changed as a result of the call). (This set will not contain the
248			* element once the call returns.)
249	dl	1.1	*
250	jsr166	1.11	* @param o object to be removed from this set, if present
251	dl	1.21	* @return {@code true} if this set contained the specified element
252	dl	1.1	* @throws ClassCastException if the specified object cannot be compared
253	jsr166	1.16	* with the elements currently in this set
254	jsr166	1.15	* @throws NullPointerException if the specified element is null
255			* and this set uses natural ordering, or its comparator
256			* does not permit null elements
257	dl	1.1	*/
258			public boolean remove(Object o) {
259			return m.remove(o)==PRESENT;
260			}
261
262			/**
263			* Removes all of the elements from this set.
264	jsr166	1.11	* The set will be empty after this call returns.
265	dl	1.1	*/
266			public void clear() {
267			m.clear();
268			}
269
270			/**
271			* Adds all of the elements in the specified collection to this set.
272			*
273	jsr166	1.14	* @param c collection containing elements to be added to this set
274	dl	1.21	* @return {@code true} if this set changed as a result of the call
275	dl	1.1	* @throws ClassCastException if the elements provided cannot be compared
276	jsr166	1.11	* with the elements currently in the set
277			* @throws NullPointerException if the specified collection is null or
278			* if any element is null and this set uses natural ordering, or
279			* its comparator does not permit null elements
280	dl	1.1	*/
281			public boolean addAll(Collection<? extends E> c) {
282			// Use linear-time version if applicable
283			if (m.size()==0 && c.size() > 0 &&
284			c instanceof SortedSet &&
285			m instanceof TreeMap) {
286	jsr166	1.9	SortedSet<? extends E> set = (SortedSet<? extends E>) c;
287	dl	1.1	TreeMap<E,Object> map = (TreeMap<E, Object>) m;
288	jsr166	1.9	Comparator<? super E> cc = (Comparator<? super E>) set.comparator();
289	dl	1.1	Comparator<? super E> mc = map.comparator();
290			if (cc==mc \|\| (cc != null && cc.equals(mc))) {
291			map.addAllForTreeSet(set, PRESENT);
292			return true;
293			}
294			}
295			return super.addAll(c);
296			}
297
298			/**
299	jsr166	1.11	* @throws ClassCastException {@inheritDoc}
300	dl	1.21	* @throws NullPointerException if {@code fromElement} or {@code toElement}
301			* is null and this set uses natural ordering, or its comparator
302			* does not permit null elements
303	jsr166	1.11	* @throws IllegalArgumentException {@inheritDoc}
304	jsr166	1.17	* @since 1.6
305	dl	1.1	*/
306	dl	1.21	public NavigableSet<E> navigableSubSet(E fromElement, boolean fromInclusive,
307			E toElement, boolean toInclusive) {
308			return new TreeSet<E>(m.navigableSubMap(fromElement, fromInclusive,
309			toElement, toInclusive));
310	dl	1.1	}
311
312			/**
313	jsr166	1.11	* @throws ClassCastException {@inheritDoc}
314	dl	1.21	* @throws NullPointerException if {@code toElement} is null and
315	jsr166	1.11	* this set uses natural ordering, or its comparator does
316			* not permit null elements
317			* @throws IllegalArgumentException {@inheritDoc}
318	jsr166	1.17	* @since 1.6
319	dl	1.1	*/
320	dl	1.21	public NavigableSet<E> navigableHeadSet(E toElement, boolean inclusive) {
321			return new TreeSet<E>(m.navigableHeadMap(toElement, inclusive));
322	dl	1.1	}
323
324			/**
325	jsr166	1.11	* @throws ClassCastException {@inheritDoc}
326	dl	1.21	* @throws NullPointerException if {@code fromElement} is null and
327	jsr166	1.11	* this set uses natural ordering, or its comparator does
328			* not permit null elements
329			* @throws IllegalArgumentException {@inheritDoc}
330	jsr166	1.17	* @since 1.6
331	dl	1.1	*/
332	dl	1.21	public NavigableSet<E> navigableTailSet(E fromElement, boolean inclusive) {
333			return new TreeSet<E>(m.navigableTailMap(fromElement, inclusive));
334	dl	1.3	}
335
336			/**
337	jsr166	1.11	* @throws ClassCastException {@inheritDoc}
338	dl	1.21	* @throws NullPointerException if {@code fromElement} or
339			* {@code toElement} is null and this set uses natural ordering,
340	jsr166	1.11	* or its comparator does not permit null elements
341			* @throws IllegalArgumentException {@inheritDoc}
342	dl	1.3	*/
343			public SortedSet<E> subSet(E fromElement, E toElement) {
344	dl	1.21	return navigableSubSet(fromElement, true, toElement, false);
345	dl	1.3	}
346
347			/**
348	jsr166	1.11	* @throws ClassCastException {@inheritDoc}
349	dl	1.21	* @throws NullPointerException if {@code toElement} is null
350	jsr166	1.11	* and this set uses natural ordering, or its comparator does
351			* not permit null elements
352			* @throws IllegalArgumentException {@inheritDoc}
353	dl	1.3	*/
354			public SortedSet<E> headSet(E toElement) {
355	dl	1.21	return navigableHeadSet(toElement, false);
356	dl	1.3	}
357
358			/**
359	jsr166	1.11	* @throws ClassCastException {@inheritDoc}
360	dl	1.21	* @throws NullPointerException if {@code fromElement} is null
361	jsr166	1.11	* and this set uses natural ordering, or its comparator does
362			* not permit null elements
363			* @throws IllegalArgumentException {@inheritDoc}
364	dl	1.3	*/
365			public SortedSet<E> tailSet(E fromElement) {
366	dl	1.21	return navigableTailSet(fromElement, true);
367	dl	1.1	}
368
369			public Comparator<? super E> comparator() {
370			return m.comparator();
371			}
372
373			/**
374	jsr166	1.11	* @throws NoSuchElementException {@inheritDoc}
375	dl	1.1	*/
376			public E first() {
377			return m.firstKey();
378			}
379
380			/**
381	jsr166	1.11	* @throws NoSuchElementException {@inheritDoc}
382	dl	1.1	*/
383			public E last() {
384			return m.lastKey();
385			}
386
387			// NavigableSet API methods
388
389			/**
390	jsr166	1.11	* @throws ClassCastException {@inheritDoc}
391	jsr166	1.15	* @throws NullPointerException if the specified element is null
392			* and this set uses natural ordering, or its comparator
393			* does not permit null elements
394	jsr166	1.17	* @since 1.6
395	dl	1.1	*/
396	jsr166	1.11	public E lower(E e) {
397			return m.lowerKey(e);
398	dl	1.1	}
399
400			/**
401	jsr166	1.11	* @throws ClassCastException {@inheritDoc}
402	jsr166	1.15	* @throws NullPointerException if the specified element is null
403			* and this set uses natural ordering, or its comparator
404			* does not permit null elements
405	jsr166	1.17	* @since 1.6
406	dl	1.1	*/
407	jsr166	1.11	public E floor(E e) {
408			return m.floorKey(e);
409	dl	1.1	}
410
411			/**
412	jsr166	1.11	* @throws ClassCastException {@inheritDoc}
413	jsr166	1.15	* @throws NullPointerException if the specified element is null
414			* and this set uses natural ordering, or its comparator
415			* does not permit null elements
416	jsr166	1.17	* @since 1.6
417	dl	1.1	*/
418	jsr166	1.11	public E ceiling(E e) {
419			return m.ceilingKey(e);
420	dl	1.1	}
421
422			/**
423	jsr166	1.11	* @throws ClassCastException {@inheritDoc}
424	jsr166	1.15	* @throws NullPointerException if the specified element is null
425			* and this set uses natural ordering, or its comparator
426			* does not permit null elements
427	jsr166	1.17	* @since 1.6
428	dl	1.1	*/
429	jsr166	1.7	public E higher(E e) {
430			return m.higherKey(e);
431	dl	1.1	}
432
433	jsr166	1.17	/**
434			* @since 1.6
435			*/
436	dl	1.1	public E pollFirst() {
437			Map.Entry<E,?> e = m.pollFirstEntry();
438			return (e == null)? null : e.getKey();
439			}
440
441	jsr166	1.17	/**
442			* @since 1.6
443			*/
444	dl	1.1	public E pollLast() {
445			Map.Entry<E,?> e = m.pollLastEntry();
446			return (e == null)? null : e.getKey();
447			}
448
449			/**
450	dl	1.21	* Returns a shallow copy of this {@code TreeSet} instance. (The elements
451	dl	1.1	* themselves are not cloned.)
452			*
453	jsr166	1.11	* @return a shallow copy of this set
454	dl	1.1	*/
455			public Object clone() {
456			TreeSet<E> clone = null;
457			try {
458			clone = (TreeSet<E>) super.clone();
459			} catch (CloneNotSupportedException e) {
460			throw new InternalError();
461			}
462
463			clone.m = new TreeMap<E,Object>(m);
464			return clone;
465			}
466
467			/**
468	dl	1.21	* Save the state of the {@code TreeSet} instance to a stream (that is,
469	dl	1.1	* serialize it).
470			*
471			* @serialData Emits the comparator used to order this set, or
472	dl	1.21	* {@code null} if it obeys its elements' natural ordering
473	jsr166	1.11	* (Object), followed by the size of the set (the number of
474			* elements it contains) (int), followed by all of its
475			* elements (each an Object) in order (as determined by the
476			* set's Comparator, or by the elements' natural ordering if
477	dl	1.1	* the set has no Comparator).
478			*/
479			private void writeObject(java.io.ObjectOutputStream s)
480			throws java.io.IOException {
481			// Write out any hidden stuff
482			s.defaultWriteObject();
483
484			// Write out Comparator
485			s.writeObject(m.comparator());
486
487			// Write out size
488			s.writeInt(m.size());
489
490			// Write out all elements in the proper order.
491			for (Iterator i=m.keySet().iterator(); i.hasNext(); )
492			s.writeObject(i.next());
493			}
494
495			/**
496	dl	1.21	* Reconstitute the {@code TreeSet} instance from a stream (that is,
497	dl	1.1	* deserialize it).
498			*/
499			private void readObject(java.io.ObjectInputStream s)
500			throws java.io.IOException, ClassNotFoundException {
501			// Read in any hidden stuff
502			s.defaultReadObject();
503
504			// Read in Comparator
505	jsr166	1.9	Comparator<? super E> c = (Comparator<? super E>) s.readObject();
506	dl	1.1
507			// Create backing TreeMap
508			TreeMap<E,Object> tm;
509			if (c==null)
510			tm = new TreeMap<E,Object>();
511			else
512			tm = new TreeMap<E,Object>(c);
513			m = tm;
514
515			// Read in size
516			int size = s.readInt();
517
518			tm.readTreeSet(size, s, PRESENT);
519			}
520
521			private static final long serialVersionUID = -2479143000061671589L;
522			}