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;
import java.util.*; // for javadoc (till 6280605 is fixed)

/**
 * 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 (<tt>add</tt>, <tt>remove</tt> and <tt>contains</tt>).
 *
 * <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 <tt>Set</tt> interface.  (See <tt>Comparable</tt>
 * or <tt>Comparator</tt> for a precise definition of <i>consistent with
 * equals</i>.)  This is so because the <tt>Set</tt> interface is defined in
 * terms of the <tt>equals</tt> operation, but a <tt>TreeSet</tt> instance
 * performs all element comparisons using its <tt>compareTo</tt> (or
 * <tt>compare</tt>) 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 <tt>Set</tt> 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 <tt>iterator</tt> 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 <tt>remove</tt>
 * 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 <tt>ConcurrentModificationException</tt> 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
{
    private transient NavigableMap<E,Object> m; // The backing Map

    // 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.
     */
    private 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>: <tt>e1.compareTo(e2)</tt> must not throw a
     * <tt>ClassCastException</tt> for any elements <tt>e1</tt> and
     * <tt>e2</tt> 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 <tt>add(Object)</tt> call will throw a
     * <tt>ClassCastException</tt>.
     */
    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: <tt>comparator.compare(e1,
     * e2)</tt> must not throw a <tt>ClassCastException</tt> for any elements
     * <tt>e1</tt> and <tt>e2</tt> in the set.  If the user attempts to add
     * an element to the set that violates this constraint, the
     * <tt>add(Object)</tt> call will throw a <tt>ClassCastException</tt>.
     *
     * @param comparator the comparator that will be used to order this set.
     *        If <tt>null</tt>, 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>: <tt>e1.compareTo(e2)</tt> must not throw a
     * <tt>ClassCastException</tt> for any elements <tt>e1</tt> and
     * <tt>e2</tt> in the set.
     *
     * @param c collection whose elements will comprise the new set
     * @throws ClassCastException if the elements in <tt>c</tt> 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.keySet().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();
    }

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

    /**
     * Returns <tt>true</tt> if this set contains the specified element.
     * More formally, returns <tt>true</tt> if and only if this set
     * contains an element <tt>e</tt> such that
     * <tt>(o==null&nbsp;?&nbsp;e==null&nbsp;:&nbsp;o.equals(e))</tt>.
     *
     * @param o object to be checked for containment in this set
     * @return <tt>true</tt> 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 <tt>e</tt> to this set if
     * the set contains no element <tt>e2</tt> such that
     * <tt>(e==null&nbsp;?&nbsp;e2==null&nbsp;:&nbsp;e.equals(e2))</tt>.
     * If this set already contains the element, the call leaves the set
     * unchanged and returns <tt>false</tt>.
     *
     * @param e element to be added to this set
     * @return <tt>true</tt> 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 <tt>e</tt> such that
     * <tt>(o==null&nbsp;?&nbsp;e==null&nbsp;:&nbsp;o.equals(e))</tt>,
     * if this set contains such an element.  Returns <tt>true</tt> 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 <tt>true</tt> 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 <tt>true</tt> 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 <tt>fromElement</tt> or
     *         <tt>toElement</tt> 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, E toElement) {
        return new TreeSet<E>(m.navigableSubMap(fromElement, toElement));
    }

    /**
     * @throws ClassCastException {@inheritDoc}
     * @throws NullPointerException if <tt>toElement</tt> 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) {
        return new TreeSet<E>(m.navigableHeadMap(toElement));
    }

    /**
     * @throws ClassCastException {@inheritDoc}
     * @throws NullPointerException if <tt>fromElement</tt> 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) {
        return new TreeSet<E>(m.navigableTailMap(fromElement));
    }

    /**
     * Equivalent to {@link #navigableSubSet} but with a return type
     * conforming to the <tt>SortedSet</tt> interface.
     *
     * <p>{@inheritDoc}
     *
     * @throws ClassCastException {@inheritDoc}
     * @throws NullPointerException if <tt>fromElement</tt> or
     *         <tt>toElement</tt> 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 new TreeSet<E>(m.navigableSubMap(fromElement, toElement));
    }

    /**
     * Equivalent to {@link #navigableHeadSet} but with a return type
     * conforming to the <tt>SortedSet</tt> interface.
     *
     * <p>{@inheritDoc}
     *
     * @throws ClassCastException {@inheritDoc}
     * @throws NullPointerException if <tt>toElement</tt> 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 new TreeSet<E>(m.navigableHeadMap(toElement));
    }

    /**
     * Equivalent to {@link #navigableTailSet} but with a return type
     * conforming to the <tt>SortedSet</tt> interface.
     *
     * <p>{@inheritDoc}
     *
     * @throws ClassCastException {@inheritDoc}
     * @throws NullPointerException if <tt>fromElement</tt> 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 new TreeSet<E>(m.navigableTailMap(fromElement));
    }

    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 <tt>TreeSet</tt> 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 <tt>TreeSet</tt> instance to a stream (that is,
     * serialize it).
     *
     * @serialData Emits the comparator used to order this set, or
     *             <tt>null</tt> 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 <tt>TreeSet</tt> 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:	1.19
Committed:	Mon Dec 5 02:56:59 2005 UTC (18 years, 5 months ago) by jsr166
Branch:	MAIN
Changes since 1.18:	+1 -1 lines
Log Message:	copyright update for 2006
#	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	jsr166	1.16	import java.util.*; // for javadoc (till 6280605 is fixed)
10	dl	1.1
11			/**
12	jsr166	1.11	* A {@link NavigableSet} implementation based on a {@link TreeMap}.
13			* The elements are ordered using their {@linkplain Comparable natural
14			* ordering}, or by a {@link Comparator} provided at set creation
15			* time, depending on which constructor is used.
16	dl	1.1	*
17	jsr166	1.11	* <p>This implementation provides guaranteed log(n) time cost for the basic
18			* operations (<tt>add</tt>, <tt>remove</tt> and <tt>contains</tt>).
19	dl	1.1	*
20	jsr166	1.11	* <p>Note that the ordering maintained by a set (whether or not an explicit
21	dl	1.1	* comparator is provided) must be <i>consistent with equals</i> if it is to
22			* correctly implement the <tt>Set</tt> interface. (See <tt>Comparable</tt>
23			* or <tt>Comparator</tt> for a precise definition of <i>consistent with
24			* equals</i>.) This is so because the <tt>Set</tt> interface is defined in
25			* terms of the <tt>equals</tt> operation, but a <tt>TreeSet</tt> instance
26	jsr166	1.11	* performs all element comparisons using its <tt>compareTo</tt> (or
27			* <tt>compare</tt>) method, so two elements that are deemed equal by this method
28	dl	1.1	* are, from the standpoint of the set, equal. The behavior of a set
29			* <i>is</i> well-defined even if its ordering is inconsistent with equals; it
30	jsr166	1.11	* just fails to obey the general contract of the <tt>Set</tt> interface.
31	dl	1.1	*
32	jsr166	1.18	* <p><strong>Note that this implementation is not synchronized.</strong>
33			* If multiple threads access a tree set concurrently, and at least one
34			* of the threads modifies the set, it <i>must</i> be synchronized
35			* externally. This is typically accomplished by synchronizing on some
36			* object that naturally encapsulates the set.
37			* If no such object exists, the set should be "wrapped" using the
38			* {@link Collections#synchronizedSortedSet Collections.synchronizedSortedSet}
39			* method. This is best done at creation time, to prevent accidental
40			* unsynchronized access to the set: <pre>
41			* SortedSet s = Collections.synchronizedSortedSet(new TreeSet(...));</pre>
42	dl	1.1	*
43	jsr166	1.11	* <p>The iterators returned by this class's <tt>iterator</tt> method are
44	dl	1.1	* <i>fail-fast</i>: if the set is modified at any time after the iterator is
45			* created, in any way except through the iterator's own <tt>remove</tt>
46	jsr166	1.11	* method, the iterator will throw a {@link ConcurrentModificationException}.
47	dl	1.1	* Thus, in the face of concurrent modification, the iterator fails quickly
48			* and cleanly, rather than risking arbitrary, non-deterministic behavior at
49			* an undetermined time in the future.
50			*
51			* <p>Note that the fail-fast behavior of an iterator cannot be guaranteed
52			* as it is, generally speaking, impossible to make any hard guarantees in the
53			* presence of unsynchronized concurrent modification. Fail-fast iterators
54			* throw <tt>ConcurrentModificationException</tt> on a best-effort basis.
55			* Therefore, it would be wrong to write a program that depended on this
56			* exception for its correctness: <i>the fail-fast behavior of iterators
57	jsr166	1.10	* should be used only to detect bugs.</i>
58	dl	1.1	*
59	jsr166	1.10	* <p>This class is a member of the
60	dl	1.1	* <a href="{@docRoot}/../guide/collections/index.html">
61			* Java Collections Framework</a>.
62			*
63	jsr166	1.11	* @param <E> the type of elements maintained by this set
64			*
65	dl	1.1	* @author Josh Bloch
66			* @version %I%, %G%
67			* @see Collection
68			* @see Set
69			* @see HashSet
70			* @see Comparable
71			* @see Comparator
72			* @see TreeMap
73			* @since 1.2
74			*/
75
76			public class TreeSet<E>
77			extends AbstractSet<E>
78			implements NavigableSet<E>, Cloneable, java.io.Serializable
79			{
80			private transient NavigableMap<E,Object> m; // The backing Map
81
82			// Dummy value to associate with an Object in the backing Map
83			private static final Object PRESENT = new Object();
84
85			/**
86	jsr166	1.11	* Constructs a set backed by the specified navigable map.
87	dl	1.1	*/
88			private TreeSet(NavigableMap<E,Object> m) {
89			this.m = m;
90			}
91
92			/**
93	jsr166	1.11	* Constructs a new, empty tree set, sorted according to the
94			* natural ordering of its elements. All elements inserted into
95			* the set must implement the {@link Comparable} interface.
96			* Furthermore, all such elements must be <i>mutually
97			* comparable</i>: <tt>e1.compareTo(e2)</tt> must not throw a
98	dl	1.1	* <tt>ClassCastException</tt> for any elements <tt>e1</tt> and
99	jsr166	1.11	* <tt>e2</tt> in the set. If the user attempts to add an element
100			* to the set that violates this constraint (for example, the user
101			* attempts to add a string element to a set whose elements are
102			* integers), the <tt>add(Object)</tt> call will throw a
103			* <tt>ClassCastException</tt>.
104	dl	1.1	*/
105			public TreeSet() {
106			this(new TreeMap<E,Object>());
107			}
108
109			/**
110	jsr166	1.12	* Constructs a new, empty tree set, sorted according to the specified
111			* comparator. All elements inserted into the set must be <i>mutually
112			* comparable</i> by the specified comparator: <tt>comparator.compare(e1,
113			* e2)</tt> must not throw a <tt>ClassCastException</tt> for any elements
114			* <tt>e1</tt> and <tt>e2</tt> in the set. If the user attempts to add
115			* an element to the set that violates this constraint, the
116			* <tt>add(Object)</tt> call will throw a <tt>ClassCastException</tt>.
117	jsr166	1.11	*
118			* @param comparator the comparator that will be used to order this set.
119			* If <tt>null</tt>, the {@linkplain Comparable natural
120			* ordering} of the elements will be used.
121			*/
122			public TreeSet(Comparator<? super E> comparator) {
123			this(new TreeMap<E,Object>(comparator));
124	dl	1.1	}
125
126			/**
127	jsr166	1.12	* Constructs a new tree set containing the elements in the specified
128			* collection, sorted according to the <i>natural ordering</i> of its
129			* elements. All elements inserted into the set must implement the
130			* {@link Comparable} interface. Furthermore, all such elements must be
131			* <i>mutually comparable</i>: <tt>e1.compareTo(e2)</tt> must not throw a
132	jsr166	1.11	* <tt>ClassCastException</tt> for any elements <tt>e1</tt> and
133			* <tt>e2</tt> in the set.
134			*
135			* @param c collection whose elements will comprise the new set
136			* @throws ClassCastException if the elements in <tt>c</tt> are
137			* not {@link Comparable}, or are not mutually comparable
138			* @throws NullPointerException if the specified collection is null
139	dl	1.1	*/
140			public TreeSet(Collection<? extends E> c) {
141			this();
142			addAll(c);
143			}
144
145			/**
146	jsr166	1.11	* Constructs a new tree set containing the same elements and
147			* using the same ordering as the specified sorted set.
148	dl	1.1	*
149	jsr166	1.11	* @param s sorted set whose elements will comprise the new set
150			* @throws NullPointerException if the specified sorted set is null
151	dl	1.1	*/
152			public TreeSet(SortedSet<E> s) {
153			this(s.comparator());
154			addAll(s);
155			}
156
157			/**
158	jsr166	1.13	* Returns an iterator over the elements in this set in ascending order.
159	dl	1.1	*
160	jsr166	1.13	* @return an iterator over the elements in this set in ascending order
161	dl	1.1	*/
162			public Iterator<E> iterator() {
163	jsr166	1.11	return m.keySet().iterator();
164	dl	1.1	}
165
166			/**
167	jsr166	1.13	* Returns an iterator over the elements in this set in descending order.
168	dl	1.1	*
169	jsr166	1.13	* @return an iterator over the elements in this set in descending order
170	jsr166	1.17	* @since 1.6
171	dl	1.1	*/
172			public Iterator<E> descendingIterator() {
173			return m.descendingKeySet().iterator();
174			}
175
176			/**
177			* Returns the number of elements in this set (its cardinality).
178			*
179	jsr166	1.11	* @return the number of elements in this set (its cardinality)
180	dl	1.1	*/
181			public int size() {
182			return m.size();
183			}
184
185			/**
186			* Returns <tt>true</tt> if this set contains no elements.
187			*
188	jsr166	1.11	* @return <tt>true</tt> if this set contains no elements
189	dl	1.1	*/
190			public boolean isEmpty() {
191			return m.isEmpty();
192			}
193
194			/**
195			* Returns <tt>true</tt> if this set contains the specified element.
196	jsr166	1.16	* More formally, returns <tt>true</tt> if and only if this set
197			* contains an element <tt>e</tt> such that
198			* <tt>(o==null ? e==null : o.equals(e))</tt>.
199	dl	1.1	*
200	jsr166	1.16	* @param o object to be checked for containment in this set
201	jsr166	1.11	* @return <tt>true</tt> if this set contains the specified element
202	dl	1.1	* @throws ClassCastException if the specified object cannot be compared
203	jsr166	1.11	* with the elements currently in the set
204	jsr166	1.15	* @throws NullPointerException if the specified element is null
205			* and this set uses natural ordering, or its comparator
206			* does not permit null elements
207	dl	1.1	*/
208			public boolean contains(Object o) {
209			return m.containsKey(o);
210			}
211
212			/**
213			* Adds the specified element to this set if it is not already present.
214	jsr166	1.16	* More formally, adds the specified element <tt>e</tt> to this set if
215			* the set contains no element <tt>e2</tt> such that
216			* <tt>(e==null ? e2==null : e.equals(e2))</tt>.
217			* If this set already contains the element, the call leaves the set
218			* unchanged and returns <tt>false</tt>.
219	dl	1.1	*
220	jsr166	1.11	* @param e element to be added to this set
221	jsr166	1.16	* @return <tt>true</tt> if this set did not already contain the specified
222	jsr166	1.11	* element
223	dl	1.1	* @throws ClassCastException if the specified object cannot be compared
224	jsr166	1.16	* with the elements currently in this set
225	jsr166	1.15	* @throws NullPointerException if the specified element is null
226			* and this set uses natural ordering, or its comparator
227			* does not permit null elements
228	dl	1.1	*/
229	jsr166	1.7	public boolean add(E e) {
230			return m.put(e, PRESENT)==null;
231	dl	1.1	}
232
233			/**
234			* Removes the specified element from this set if it is present.
235	jsr166	1.16	* More formally, removes an element <tt>e</tt> such that
236			* <tt>(o==null ? e==null : o.equals(e))</tt>,
237			* if this set contains such an element. Returns <tt>true</tt> if
238			* this set contained the element (or equivalently, if this set
239			* changed as a result of the call). (This set will not contain the
240			* element once the call returns.)
241	dl	1.1	*
242	jsr166	1.11	* @param o object to be removed from this set, if present
243	jsr166	1.16	* @return <tt>true</tt> if this set contained the specified element
244	dl	1.1	* @throws ClassCastException if the specified object cannot be compared
245	jsr166	1.16	* with the elements currently in this set
246	jsr166	1.15	* @throws NullPointerException if the specified element is null
247			* and this set uses natural ordering, or its comparator
248			* does not permit null elements
249	dl	1.1	*/
250			public boolean remove(Object o) {
251			return m.remove(o)==PRESENT;
252			}
253
254			/**
255			* Removes all of the elements from this set.
256	jsr166	1.11	* The set will be empty after this call returns.
257	dl	1.1	*/
258			public void clear() {
259			m.clear();
260			}
261
262			/**
263			* Adds all of the elements in the specified collection to this set.
264			*
265	jsr166	1.14	* @param c collection containing elements to be added to this set
266	jsr166	1.11	* @return <tt>true</tt> if this set changed as a result of the call
267	dl	1.1	* @throws ClassCastException if the elements provided cannot be compared
268	jsr166	1.11	* with the elements currently in the set
269			* @throws NullPointerException if the specified collection is null or
270			* if any element is null and this set uses natural ordering, or
271			* its comparator does not permit null elements
272	dl	1.1	*/
273			public boolean addAll(Collection<? extends E> c) {
274			// Use linear-time version if applicable
275			if (m.size()==0 && c.size() > 0 &&
276			c instanceof SortedSet &&
277			m instanceof TreeMap) {
278	jsr166	1.9	SortedSet<? extends E> set = (SortedSet<? extends E>) c;
279	dl	1.1	TreeMap<E,Object> map = (TreeMap<E, Object>) m;
280	jsr166	1.9	Comparator<? super E> cc = (Comparator<? super E>) set.comparator();
281	dl	1.1	Comparator<? super E> mc = map.comparator();
282			if (cc==mc \|\| (cc != null && cc.equals(mc))) {
283			map.addAllForTreeSet(set, PRESENT);
284			return true;
285			}
286			}
287			return super.addAll(c);
288			}
289
290			/**
291	jsr166	1.11	* @throws ClassCastException {@inheritDoc}
292	dl	1.1	* @throws NullPointerException if <tt>fromElement</tt> or
293	jsr166	1.11	* <tt>toElement</tt> is null and this set uses natural ordering,
294			* or its comparator does not permit null elements
295			* @throws IllegalArgumentException {@inheritDoc}
296	jsr166	1.17	* @since 1.6
297	dl	1.1	*/
298	dl	1.3	public NavigableSet<E> navigableSubSet(E fromElement, E toElement) {
299			return new TreeSet<E>(m.navigableSubMap(fromElement, toElement));
300	dl	1.1	}
301
302			/**
303	jsr166	1.11	* @throws ClassCastException {@inheritDoc}
304			* @throws NullPointerException if <tt>toElement</tt> is null and
305			* this set uses natural ordering, or its comparator does
306			* not permit null elements
307			* @throws IllegalArgumentException {@inheritDoc}
308	jsr166	1.17	* @since 1.6
309	dl	1.1	*/
310	dl	1.3	public NavigableSet<E> navigableHeadSet(E toElement) {
311			return new TreeSet<E>(m.navigableHeadMap(toElement));
312	dl	1.1	}
313
314			/**
315	jsr166	1.11	* @throws ClassCastException {@inheritDoc}
316			* @throws NullPointerException if <tt>fromElement</tt> is null and
317			* this set uses natural ordering, or its comparator does
318			* not permit null elements
319			* @throws IllegalArgumentException {@inheritDoc}
320	jsr166	1.17	* @since 1.6
321	dl	1.1	*/
322	dl	1.3	public NavigableSet<E> navigableTailSet(E fromElement) {
323			return new TreeSet<E>(m.navigableTailMap(fromElement));
324			}
325
326			/**
327	jsr166	1.11	* Equivalent to {@link #navigableSubSet} but with a return type
328			* conforming to the <tt>SortedSet</tt> interface.
329			*
330			* <p>{@inheritDoc}
331			*
332			* @throws ClassCastException {@inheritDoc}
333	dl	1.3	* @throws NullPointerException if <tt>fromElement</tt> or
334	jsr166	1.11	* <tt>toElement</tt> is null and this set uses natural ordering,
335			* or its comparator does not permit null elements
336			* @throws IllegalArgumentException {@inheritDoc}
337	dl	1.3	*/
338			public SortedSet<E> subSet(E fromElement, E toElement) {
339			return new TreeSet<E>(m.navigableSubMap(fromElement, toElement));
340			}
341
342			/**
343	jsr166	1.11	* Equivalent to {@link #navigableHeadSet} but with a return type
344			* conforming to the <tt>SortedSet</tt> interface.
345			*
346			* <p>{@inheritDoc}
347	dl	1.3	*
348	jsr166	1.11	* @throws ClassCastException {@inheritDoc}
349			* @throws NullPointerException if <tt>toElement</tt> is null
350			* 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			return new TreeSet<E>(m.navigableHeadMap(toElement));
356			}
357
358			/**
359	jsr166	1.11	* Equivalent to {@link #navigableTailSet} but with a return type
360			* conforming to the <tt>SortedSet</tt> interface.
361			*
362			* <p>{@inheritDoc}
363			*
364			* @throws ClassCastException {@inheritDoc}
365			* @throws NullPointerException if <tt>fromElement</tt> is null
366			* and this set uses natural ordering, or its comparator does
367			* not permit null elements
368			* @throws IllegalArgumentException {@inheritDoc}
369	dl	1.3	*/
370			public SortedSet<E> tailSet(E fromElement) {
371			return new TreeSet<E>(m.navigableTailMap(fromElement));
372	dl	1.1	}
373
374			public Comparator<? super E> comparator() {
375			return m.comparator();
376			}
377
378			/**
379	jsr166	1.11	* @throws NoSuchElementException {@inheritDoc}
380	dl	1.1	*/
381			public E first() {
382			return m.firstKey();
383			}
384
385			/**
386	jsr166	1.11	* @throws NoSuchElementException {@inheritDoc}
387	dl	1.1	*/
388			public E last() {
389			return m.lastKey();
390			}
391
392			// NavigableSet API methods
393
394			/**
395	jsr166	1.11	* @throws ClassCastException {@inheritDoc}
396	jsr166	1.15	* @throws NullPointerException if the specified element is null
397			* and this set uses natural ordering, or its comparator
398			* does not permit null elements
399	jsr166	1.17	* @since 1.6
400	dl	1.1	*/
401	jsr166	1.11	public E lower(E e) {
402			return m.lowerKey(e);
403	dl	1.1	}
404
405			/**
406	jsr166	1.11	* @throws ClassCastException {@inheritDoc}
407	jsr166	1.15	* @throws NullPointerException if the specified element is null
408			* and this set uses natural ordering, or its comparator
409			* does not permit null elements
410	jsr166	1.17	* @since 1.6
411	dl	1.1	*/
412	jsr166	1.11	public E floor(E e) {
413			return m.floorKey(e);
414	dl	1.1	}
415
416			/**
417	jsr166	1.11	* @throws ClassCastException {@inheritDoc}
418	jsr166	1.15	* @throws NullPointerException if the specified element is null
419			* and this set uses natural ordering, or its comparator
420			* does not permit null elements
421	jsr166	1.17	* @since 1.6
422	dl	1.1	*/
423	jsr166	1.11	public E ceiling(E e) {
424			return m.ceilingKey(e);
425	dl	1.1	}
426
427			/**
428	jsr166	1.11	* @throws ClassCastException {@inheritDoc}
429	jsr166	1.15	* @throws NullPointerException if the specified element is null
430			* and this set uses natural ordering, or its comparator
431			* does not permit null elements
432	jsr166	1.17	* @since 1.6
433	dl	1.1	*/
434	jsr166	1.7	public E higher(E e) {
435			return m.higherKey(e);
436	dl	1.1	}
437
438	jsr166	1.17	/**
439			* @since 1.6
440			*/
441	dl	1.1	public E pollFirst() {
442			Map.Entry<E,?> e = m.pollFirstEntry();
443			return (e == null)? null : e.getKey();
444			}
445
446	jsr166	1.17	/**
447			* @since 1.6
448			*/
449	dl	1.1	public E pollLast() {
450			Map.Entry<E,?> e = m.pollLastEntry();
451			return (e == null)? null : e.getKey();
452			}
453
454			/**
455			* Returns a shallow copy of this <tt>TreeSet</tt> instance. (The elements
456			* themselves are not cloned.)
457			*
458	jsr166	1.11	* @return a shallow copy of this set
459	dl	1.1	*/
460			public Object clone() {
461			TreeSet<E> clone = null;
462			try {
463			clone = (TreeSet<E>) super.clone();
464			} catch (CloneNotSupportedException e) {
465			throw new InternalError();
466			}
467
468			clone.m = new TreeMap<E,Object>(m);
469
470			return clone;
471			}
472
473			/**
474			* Save the state of the <tt>TreeSet</tt> instance to a stream (that is,
475			* serialize it).
476			*
477			* @serialData Emits the comparator used to order this set, or
478	jsr166	1.11	* <tt>null</tt> if it obeys its elements' natural ordering
479			* (Object), followed by the size of the set (the number of
480			* elements it contains) (int), followed by all of its
481			* elements (each an Object) in order (as determined by the
482			* set's Comparator, or by the elements' natural ordering if
483	dl	1.1	* the set has no Comparator).
484			*/
485			private void writeObject(java.io.ObjectOutputStream s)
486			throws java.io.IOException {
487			// Write out any hidden stuff
488			s.defaultWriteObject();
489
490			// Write out Comparator
491			s.writeObject(m.comparator());
492
493			// Write out size
494			s.writeInt(m.size());
495
496			// Write out all elements in the proper order.
497			for (Iterator i=m.keySet().iterator(); i.hasNext(); )
498			s.writeObject(i.next());
499			}
500
501			/**
502			* Reconstitute the <tt>TreeSet</tt> instance from a stream (that is,
503			* deserialize it).
504			*/
505			private void readObject(java.io.ObjectInputStream s)
506			throws java.io.IOException, ClassNotFoundException {
507			// Read in any hidden stuff
508			s.defaultReadObject();
509
510			// Read in Comparator
511	jsr166	1.9	Comparator<? super E> c = (Comparator<? super E>) s.readObject();
512	dl	1.1
513			// Create backing TreeMap
514			TreeMap<E,Object> tm;
515			if (c==null)
516			tm = new TreeMap<E,Object>();
517			else
518			tm = new TreeMap<E,Object>(c);
519			m = tm;
520
521			// Read in size
522			int size = s.readInt();
523
524			tm.readTreeSet(size, s, PRESENT);
525			}
526
527			private static final long serialVersionUID = -2479143000061671589L;
528			}