/*
* %W% %E%
*
* Copyright 2005 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.
*
*
This implementation provides guaranteed log(n) time cost for the basic
* operations (add, remove and contains).
*
*
Note that the ordering maintained by a set (whether or not an explicit
* comparator is provided) must be consistent with equals if it is to
* correctly implement the Set interface. (See Comparable
* or Comparator for a precise definition of consistent with
* equals.) This is so because the Set interface is defined in
* terms of the equals operation, but a TreeSet instance
* performs all element comparisons using its compareTo (or
* 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
* is well-defined even if its ordering is inconsistent with equals; it
* just fails to obey the general contract of the Set interface.
*
*
Note that this implementation is not synchronized. If multiple
* threads access a set concurrently, and at least one of the threads modifies
* the set, it must 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
* Collections.synchronizedSet method. This is best done at creation
* time, to prevent accidental unsynchronized access to the set:
* SortedSet s = Collections.synchronizedSortedSet(new TreeSet(...));
*
*
* The iterators returned by this class's iterator method are
* fail-fast: if the set is modified at any time after the iterator is
* created, in any way except through the iterator's own 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.
*
*
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 ConcurrentModificationException on a best-effort basis.
* Therefore, it would be wrong to write a program that depended on this
* exception for its correctness: the fail-fast behavior of iterators
* should be used only to detect bugs.
*
*
This class is a member of the
*
* Java Collections Framework.
*
* @param 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 Collections#synchronizedSortedSet(SortedSet)
* @see TreeMap
* @since 1.2
*/
public class TreeSet
extends AbstractSet
implements NavigableSet, Cloneable, java.io.Serializable
{
private transient NavigableMap 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 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 mutually
* comparable: e1.compareTo(e2) must not throw a
* ClassCastException for any elements e1 and
* 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 add(Object) call will throw a
* ClassCastException.
*/
public TreeSet() {
this(new TreeMap());
}
/**
* Constructs a new, empty tree set, sorted according to the specified
* comparator. All elements inserted into the set must be mutually
* comparable by the specified comparator: comparator.compare(e1,
* e2) must not throw a ClassCastException for any elements
* e1 and e2 in the set. If the user attempts to add
* an element to the set that violates this constraint, the
* add(Object) call will throw a ClassCastException.
*
* @param comparator the comparator that will be used to order this set.
* If null, the {@linkplain Comparable natural
* ordering} of the elements will be used.
*/
public TreeSet(Comparator super E> comparator) {
this(new TreeMap(comparator));
}
/**
* Constructs a new tree set containing the elements in the specified
* collection, sorted according to the natural ordering of its
* elements. All elements inserted into the set must implement the
* {@link Comparable} interface. Furthermore, all such elements must be
* mutually comparable: e1.compareTo(e2) must not throw a
* ClassCastException for any elements e1 and
* e2 in the set.
*
* @param c collection whose elements will comprise the new set
* @throws ClassCastException if the elements in 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 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 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 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 true if this set contains no elements.
*
* @return true if this set contains no elements
*/
public boolean isEmpty() {
return m.isEmpty();
}
/**
* Returns true if this set contains the specified element.
* More formally, returns true if and only if this set
* contains an element e such that
* (o==null ? e==null : o.equals(e)).
*
* @param o object to be checked for containment in this set
* @return 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 e to this set if
* the set contains no element e2 such that
* (e==null ? e2==null : e.equals(e2)).
* If this set already contains the element, the call leaves the set
* unchanged and returns false.
*
* @param e element to be added to this set
* @return 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 e such that
* (o==null ? e==null : o.equals(e)),
* if this set contains such an element. Returns 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 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 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 map = (TreeMap) 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 fromElement or
* 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 navigableSubSet(E fromElement, E toElement) {
return new TreeSet(m.navigableSubMap(fromElement, toElement));
}
/**
* @throws ClassCastException {@inheritDoc}
* @throws NullPointerException if 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 navigableHeadSet(E toElement) {
return new TreeSet(m.navigableHeadMap(toElement));
}
/**
* @throws ClassCastException {@inheritDoc}
* @throws NullPointerException if 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 navigableTailSet(E fromElement) {
return new TreeSet(m.navigableTailMap(fromElement));
}
/**
* Equivalent to {@link #navigableSubSet} but with a return type
* conforming to the SortedSet interface.
*
* {@inheritDoc}
*
* @throws ClassCastException {@inheritDoc}
* @throws NullPointerException if fromElement or
* toElement is null and this set uses natural ordering,
* or its comparator does not permit null elements
* @throws IllegalArgumentException {@inheritDoc}
*/
public SortedSet subSet(E fromElement, E toElement) {
return new TreeSet(m.navigableSubMap(fromElement, toElement));
}
/**
* Equivalent to {@link #navigableHeadSet} but with a return type
* conforming to the SortedSet interface.
*
* {@inheritDoc}
*
* @throws ClassCastException {@inheritDoc}
* @throws NullPointerException if toElement is null
* and this set uses natural ordering, or its comparator does
* not permit null elements
* @throws IllegalArgumentException {@inheritDoc}
*/
public SortedSet headSet(E toElement) {
return new TreeSet(m.navigableHeadMap(toElement));
}
/**
* Equivalent to {@link #navigableTailSet} but with a return type
* conforming to the SortedSet interface.
*
* {@inheritDoc}
*
* @throws ClassCastException {@inheritDoc}
* @throws NullPointerException if fromElement is null
* and this set uses natural ordering, or its comparator does
* not permit null elements
* @throws IllegalArgumentException {@inheritDoc}
*/
public SortedSet tailSet(E fromElement) {
return new TreeSet(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 = m.pollFirstEntry();
return (e == null)? null : e.getKey();
}
/**
* @since 1.6
*/
public E pollLast() {
Map.Entry e = m.pollLastEntry();
return (e == null)? null : e.getKey();
}
/**
* Returns a shallow copy of this TreeSet instance. (The elements
* themselves are not cloned.)
*
* @return a shallow copy of this set
*/
public Object clone() {
TreeSet clone = null;
try {
clone = (TreeSet) super.clone();
} catch (CloneNotSupportedException e) {
throw new InternalError();
}
clone.m = new TreeMap(m);
return clone;
}
/**
* Save the state of the TreeSet instance to a stream (that is,
* serialize it).
*
* @serialData Emits the comparator used to order this set, or
* 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 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 tm;
if (c==null)
tm = new TreeMap();
else
tm = new TreeMap(c);
m = tm;
// Read in size
int size = s.readInt();
tm.readTreeSet(size, s, PRESENT);
}
private static final long serialVersionUID = -2479143000061671589L;
}