java.util.AbstractCollection<E>
java.util.AbstractSet<E>
java.util.TreeSet<E>
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JavaTM 2 Platform Standard Ed. 5.0 |
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java.lang.Object
public class TreeSet<E>
This class implements the Set interface, backed by a TreeMap instance. This class guarantees that the sorted set will be in ascending element order, sorted according to the natural order of the elements (see Comparable), or by the 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 key comparisons using its compareTo (or compare) method, so two keys 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 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.
Collection,
Set,
HashSet,
Comparable,
Comparator,
Collections.synchronizedSortedSet(SortedSet),
TreeMap,
Serialized Form| Constructor Summary | |
|---|---|
TreeSet()
Constructs a new, empty set, sorted according to the elements' natural order. |
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TreeSet(Collection<? extends E> c)
Constructs a new set containing the elements in the specified collection, sorted according to the elements' natural order. |
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TreeSet(Comparator<? super E> c)
Constructs a new, empty set, sorted according to the specified comparator. |
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TreeSet(SortedSet<E> s)
Constructs a new set containing the same elements as the specified sorted set, sorted according to the same ordering. |
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| Method Summary | |
|---|---|
boolean |
add(E o)
Adds the specified element to this set if it is not already present. |
boolean |
addAll(Collection<? extends E> c)
Adds all of the elements in the specified collection to this set. |
void |
clear()
Removes all of the elements from this set. |
Object |
clone()
Returns a shallow copy of this TreeSet instance. |
Comparator<? super E> |
comparator()
Returns the comparator used to order this sorted set, or null if this tree set uses its elements natural ordering. |
boolean |
contains(Object o)
Returns true if this set contains the specified element. |
E |
first()
Returns the first (lowest) element currently in this sorted set. |
SortedSet<E> |
headSet(E toElement)
Returns a view of the portion of this set whose elements are strictly less than toElement. |
boolean |
isEmpty()
Returns true if this set contains no elements. |
Iterator<E> |
iterator()
Returns an iterator over the elements in this set. |
E |
last()
Returns the last (highest) element currently in this sorted set. |
boolean |
remove(Object o)
Removes the specified element from this set if it is present. |
int |
size()
Returns the number of elements in this set (its cardinality). |
SortedSet<E> |
subSet(E fromElement,
E toElement)
Returns a view of the portion of this set whose elements range from fromElement, inclusive, to toElement, exclusive. |
SortedSet<E> |
tailSet(E fromElement)
Returns a view of the portion of this set whose elements are greater than or equal to fromElement. |
| Methods inherited from class java.util.AbstractSet |
|---|
equals, hashCode, removeAll |
| Methods inherited from class java.util.AbstractCollection |
|---|
containsAll, retainAll, toArray, toArray, toString |
| Methods inherited from class java.lang.Object |
|---|
finalize, getClass, notify, notifyAll, wait, wait, wait |
| Methods inherited from interface java.util.Set |
|---|
containsAll, equals, hashCode, removeAll, retainAll, toArray, toArray |
| Constructor Detail |
|---|
public TreeSet()
Comparablepublic TreeSet(Comparator<? super E> c)
c - the comparator that will be used to sort this set. A
null value indicates that the elements' natural
ordering should be used.public TreeSet(Collection<? extends E> c)
c - The elements that will comprise the new set.
ClassCastException - if the keys in the specified collection are
not comparable, or are not mutually comparable.
NullPointerException - if the specified collection is null.public TreeSet(SortedSet<E> s)
s - sorted set whose elements will comprise the new set.
NullPointerException - if the specified sorted set is null.| Method Detail |
|---|
public Iterator<E> iterator()
iterator in interface Iterable<E>iterator in interface Collection<E>iterator in interface Set<E>iterator in class AbstractCollection<E>public int size()
size in interface Collection<E>size in interface Set<E>size in class AbstractCollection<E>public boolean isEmpty()
isEmpty in interface Collection<E>isEmpty in interface Set<E>isEmpty in class AbstractCollection<E>public boolean contains(Object o)
contains in interface Collection<E>contains in interface Set<E>contains in class AbstractCollection<E>o - the object to be checked for containment in this set.
ClassCastException - if the specified object cannot be compared
with the elements currently in the set.public boolean add(E o)
add in interface Collection<E>add in interface Set<E>add in class AbstractCollection<E>o - element to be added to this set.
ClassCastException - if the specified object cannot be compared
with the elements currently in the set.public boolean remove(Object o)
remove in interface Collection<E>remove in interface Set<E>remove in class AbstractCollection<E>o - object to be removed from this set, if present.
ClassCastException - if the specified object cannot be compared
with the elements currently in the set.public void clear()
clear in interface Collection<E>clear in interface Set<E>clear in class AbstractCollection<E>public boolean addAll(Collection<? extends E> c)
addAll in interface Collection<E>addAll in interface Set<E>addAll in class AbstractCollection<E>c - elements to be added
ClassCastException - if the elements provided cannot be compared
with the elements currently in the set.
NullPointerException - of the specified collection is null.AbstractCollection.add(Object)
public SortedSet<E> subSet(E fromElement,
E toElement)
The sorted set returned by this method will throw an IllegalArgumentException if the user attempts to insert an element outside the specified range.
Note: this method always returns a half-open range (which includes its low endpoint but not its high endpoint). If you need a closed range (which includes both endpoints), and the element type allows for calculation of the successor of a specified value, merely request the subrange from lowEndpoint to successor(highEndpoint). For example, suppose that s is a sorted set of strings. The following idiom obtains a view containing all of the strings in s from low to high, inclusive:
SortedSet sub = s.subSet(low, high+"\0");
A similar technique can be used to generate an open range (which
contains neither endpoint). The following idiom obtains a view
containing all of the strings in s from low to
high, exclusive:
SortedSet sub = s.subSet(low+"\0", high);
subSet in interface SortedSet<E>fromElement - low endpoint (inclusive) of the subSet.toElement - high endpoint (exclusive) of the subSet.
ClassCastException - if fromElement and
toElement cannot be compared to one another using
this set's comparator (or, if the set has no comparator,
using natural ordering).
IllegalArgumentException - if fromElement is greater than
toElement.
NullPointerException - if fromElement or
toElement is null and this set uses natural
order, or its comparator does not tolerate null
elements.public SortedSet<E> headSet(E toElement)
The sorted set returned by this method will throw an IllegalArgumentException if the user attempts to insert an element greater than or equal to toElement.
Note: this method always returns a view that does not contain its (high) endpoint. If you need a view that does contain this endpoint, and the element type allows for calculation of the successor of a specified value, merely request a headSet bounded by successor(highEndpoint). For example, suppose that s is a sorted set of strings. The following idiom obtains a view containing all of the strings in s that are less than or equal to high:
SortedSet head = s.headSet(high+"\0");
headSet in interface SortedSet<E>toElement - high endpoint (exclusive) of the headSet.
ClassCastException - if toElement is not compatible
with this set's comparator (or, if the set has no comparator,
if toElement does not implement Comparable).
IllegalArgumentException - if this set is itself a subSet,
headSet, or tailSet, and toElement is not within the
specified range of the subSet, headSet, or tailSet.
NullPointerException - if toElement is null and
this set uses natural ordering, or its comparator does
not tolerate null elements.public SortedSet<E> tailSet(E fromElement)
The sorted set returned by this method will throw an IllegalArgumentException if the user attempts to insert an element less than fromElement. Note: this method always returns a view that contains its (low) endpoint. If you need a view that does not contain this endpoint, and the element type allows for calculation of the successor of a specified value, merely request a tailSet bounded by successor(lowEndpoint). For example, suppose that s is a sorted set of strings. The following idiom obtains a view containing all of the strings in s that are strictly greater than low:
SortedSet tail = s.tailSet(low+"\0");
tailSet in interface SortedSet<E>fromElement - low endpoint (inclusive) of the tailSet.
ClassCastException - if fromElement is not compatible
with this set's comparator (or, if the set has no comparator,
if fromElement does not implement Comparable).
IllegalArgumentException - if this set is itself a subSet,
headSet, or tailSet, and fromElement is not within the
specified range of the subSet, headSet, or tailSet.
NullPointerException - if fromElement is null
and this set uses natural ordering, or its comparator does
not tolerate null elements.public Comparator<? super E> comparator()
comparator in interface SortedSet<E>public E first()
first in interface SortedSet<E>NoSuchElementException - sorted set is empty.public E last()
last in interface SortedSet<E>NoSuchElementException - sorted set is empty.public Object clone()
clone in class ObjectCloneable
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JavaTM 2 Platform Standard Ed. 5.0 |
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Copyright 2004 Sun Microsystems, Inc. All rights reserved. Use is subject to license terms. Also see the documentation redistribution policy.