TreeSet.java revision 3203
0N/A/*
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0N/A *
0N/A * This code is free software; you can redistribute it and/or modify it
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0N/A * published by the Free Software Foundation. Oracle designates this
0N/A * particular file as subject to the "Classpath" exception as provided
0N/A * by Oracle in the LICENSE file that accompanied this code.
0N/A *
0N/A * This code is distributed in the hope that it will be useful, but WITHOUT
0N/A * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
0N/A * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
0N/A * version 2 for more details (a copy is included in the LICENSE file that
0N/A * accompanied this code).
0N/A *
0N/A * You should have received a copy of the GNU General Public License version
0N/A * 2 along with this work; if not, write to the Free Software Foundation,
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1472N/A *
1472N/A * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
0N/A * or visit www.oracle.com if you need additional information or have any
0N/A * questions.
0N/A */
1879N/A
1879N/Apackage java.util;
1879N/A
1879N/A/**
1879N/A * A {@link NavigableSet} implementation based on a {@link TreeMap}.
1879N/A * The elements are ordered using their {@linkplain Comparable natural
1879N/A * ordering}, or by a {@link Comparator} provided at set creation
1879N/A * time, depending on which constructor is used.
1879N/A *
1879N/A * <p>This implementation provides guaranteed log(n) time cost for the basic
1879N/A * operations ({@code add}, {@code remove} and {@code contains}).
1879N/A *
1879N/A * <p>Note that the ordering maintained by a set (whether or not an explicit
1879N/A * comparator is provided) must be <i>consistent with equals</i> if it is to
1879N/A * correctly implement the {@code Set} interface. (See {@code Comparable}
1879N/A * or {@code Comparator} for a precise definition of <i>consistent with
1879N/A * equals</i>.) This is so because the {@code Set} interface is defined in
1879N/A * terms of the {@code equals} operation, but a {@code TreeSet} instance
1879N/A * performs all element comparisons using its {@code compareTo} (or
1879N/A * {@code compare}) method, so two elements that are deemed equal by this method
0N/A * are, from the standpoint of the set, equal. The behavior of a set
0N/A * <i>is</i> well-defined even if its ordering is inconsistent with equals; it
0N/A * just fails to obey the general contract of the {@code Set} interface.
0N/A *
0N/A * <p><strong>Note that this implementation is not synchronized.</strong>
0N/A * If multiple threads access a tree set concurrently, and at least one
0N/A * of the threads modifies the set, it <i>must</i> be synchronized
0N/A * externally. This is typically accomplished by synchronizing on some
0N/A * object that naturally encapsulates the set.
0N/A * If no such object exists, the set should be "wrapped" using the
0N/A * {@link Collections#synchronizedSortedSet Collections.synchronizedSortedSet}
0N/A * method. This is best done at creation time, to prevent accidental
1522N/A * unsynchronized access to the set: <pre>
0N/A * SortedSet s = Collections.synchronizedSortedSet(new TreeSet(...));</pre>
113N/A *
113N/A * <p>The iterators returned by this class's {@code iterator} method are
2027N/A * <i>fail-fast</i>: if the set is modified at any time after the iterator is
113N/A * created, in any way except through the iterator's own {@code remove}
0N/A * method, the iterator will throw a {@link ConcurrentModificationException}.
2027N/A * Thus, in the face of concurrent modification, the iterator fails quickly
1485N/A * and cleanly, rather than risking arbitrary, non-deterministic behavior at
2027N/A * an undetermined time in the future.
1485N/A *
2027N/A * <p>Note that the fail-fast behavior of an iterator cannot be guaranteed
1485N/A * as it is, generally speaking, impossible to make any hard guarantees in the
2027N/A * presence of unsynchronized concurrent modification. Fail-fast iterators
0N/A * throw {@code ConcurrentModificationException} on a best-effort basis.
726N/A * Therefore, it would be wrong to write a program that depended on this
726N/A * exception for its correctness: <i>the fail-fast behavior of iterators
726N/A * should be used only to detect bugs.</i>
0N/A *
0N/A * <p>This class is a member of the
941N/A * <a href="{@docRoot}/../technotes/guides/collections/index.html">
941N/A * Java Collections Framework</a>.
941N/A *
0N/A * @param <E> the type of elements maintained by this set
0N/A *
0N/A * @author Josh Bloch
1522N/A * @see Collection
0N/A * @see Set
0N/A * @see HashSet
0N/A * @see Comparable
0N/A * @see Comparator
0N/A * @see TreeMap
0N/A * @since 1.2
0N/A */
0N/A
0N/Apublic class TreeSet<E> extends AbstractSet<E>
0N/A implements NavigableSet<E>, Cloneable, java.io.Serializable
0N/A{
0N/A /**
0N/A * The backing map.
0N/A */
0N/A private transient NavigableMap<E,Object> m;
0N/A
0N/A // Dummy value to associate with an Object in the backing Map
0N/A private static final Object PRESENT = new Object();
0N/A
0N/A /**
0N/A * Constructs a set backed by the specified navigable map.
0N/A */
0N/A TreeSet(NavigableMap<E,Object> m) {
0N/A this.m = m;
0N/A }
0N/A
0N/A /**
0N/A * Constructs a new, empty tree set, sorted according to the
0N/A * natural ordering of its elements. All elements inserted into
0N/A * the set must implement the {@link Comparable} interface.
0N/A * Furthermore, all such elements must be <i>mutually
0N/A * comparable</i>: {@code e1.compareTo(e2)} must not throw a
0N/A * {@code ClassCastException} for any elements {@code e1} and
726N/A * {@code e2} in the set. If the user attempts to add an element
726N/A * to the set that violates this constraint (for example, the user
0N/A * attempts to add a string element to a set whose elements are
0N/A * integers), the {@code add} call will throw a
0N/A * {@code ClassCastException}.
0N/A */
0N/A public TreeSet() {
0N/A this(new TreeMap<E,Object>());
0N/A }
0N/A
0N/A /**
0N/A * Constructs a new, empty tree set, sorted according to the specified
0N/A * comparator. All elements inserted into the set must be <i>mutually
0N/A * comparable</i> by the specified comparator: {@code comparator.compare(e1,
0N/A * e2)} must not throw a {@code ClassCastException} for any elements
0N/A * {@code e1} and {@code e2} in the set. If the user attempts to add
0N/A * an element to the set that violates this constraint, the
0N/A * {@code add} call will throw a {@code ClassCastException}.
0N/A *
0N/A * @param comparator the comparator that will be used to order this set.
0N/A * If {@code null}, the {@linkplain Comparable natural
0N/A * ordering} of the elements will be used.
0N/A */
0N/A public TreeSet(Comparator<? super E> comparator) {
0N/A this(new TreeMap<E,Object>(comparator));
0N/A }
0N/A
2745N/A /**
2745N/A * Constructs a new tree set containing the elements in the specified
0N/A * collection, sorted according to the <i>natural ordering</i> of its
0N/A * elements. All elements inserted into the set must implement the
0N/A * {@link Comparable} interface. Furthermore, all such elements must be
0N/A * <i>mutually comparable</i>: {@code e1.compareTo(e2)} must not throw a
1879N/A * {@code ClassCastException} for any elements {@code e1} and
1879N/A * {@code e2} in the set.
1879N/A *
1879N/A * @param c collection whose elements will comprise the new set
1879N/A * @throws ClassCastException if the elements in {@code c} are
1879N/A * not {@link Comparable}, or are not mutually comparable
1879N/A * @throws NullPointerException if the specified collection is null
1879N/A */
1879N/A public TreeSet(Collection<? extends E> c) {
2073N/A this();
2073N/A addAll(c);
2073N/A }
2073N/A
2073N/A /**
2073N/A * Constructs a new tree set containing the same elements and
1879N/A * using the same ordering as the specified sorted set.
0N/A *
0N/A * @param s sorted set whose elements will comprise the new set
0N/A * @throws NullPointerException if the specified sorted set is null
0N/A */
0N/A public TreeSet(SortedSet<E> s) {
0N/A this(s.comparator());
2003N/A addAll(s);
0N/A }
0N/A
0N/A /**
0N/A * Returns an iterator over the elements in this set in ascending order.
0N/A *
0N/A * @return an iterator over the elements in this set in ascending order
0N/A */
0N/A public Iterator<E> iterator() {
0N/A return m.navigableKeySet().iterator();
0N/A }
0N/A
0N/A /**
0N/A * Returns an iterator over the elements in this set in descending order.
0N/A *
0N/A * @return an iterator over the elements in this set in descending order
0N/A * @since 1.6
0N/A */
0N/A public Iterator<E> descendingIterator() {
0N/A return m.descendingKeySet().iterator();
0N/A }
0N/A
0N/A /**
0N/A * @since 1.6
0N/A */
0N/A public NavigableSet<E> descendingSet() {
0N/A return new TreeSet<E>(m.descendingMap());
0N/A }
1879N/A
1879N/A /**
* 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
* <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 {@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
* <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 {@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
* <tt>(o==null&nbsp;?&nbsp;e==null&nbsp;:&nbsp;o.equals(e))</tt>,
* 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> subSet(E fromElement, boolean fromInclusive,
E toElement, boolean toInclusive) {
return new TreeSet<E>(m.subMap(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> headSet(E toElement, boolean inclusive) {
return new TreeSet<E>(m.headMap(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> tailSet(E fromElement, boolean inclusive) {
return new TreeSet<E>(m.tailMap(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 subSet(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 headSet(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 tailSet(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 (E e : m.keySet())
s.writeObject(e);
}
/**
* 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;
}