java.util
public class TreeSet<E> extends AbstractSet<E> implements SortedSet<E>, Cloneable, Serializable
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.
Since: 1.2
Version: 1.31, 06/22/03
See Also: Collection Set HashSet Comparable Comparator synchronizedSortedSet TreeMap
| Constructor Summary | |
|---|---|
| TreeSet()
Constructs a new, empty set, sorted according to the elements' natural
order. | |
| TreeSet(Comparator<? super E> c)
Constructs a new, empty set, sorted according to the specified
comparator. | |
| TreeSet(Collection<? extends E> c)
Constructs a new set containing the elements in the specified
collection, sorted according to the elements' natural order.
| |
| TreeSet(SortedSet<E> s)
Constructs a new set containing the same elements as the specified
sorted set, sorted according to the same ordering.
| |
| 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. |
See Also: Comparable
Parameters: c the comparator that will be used to sort this set. A null value indicates that the elements' natural ordering should be used.
Parameters: c The elements that will comprise the new set.
Throws: ClassCastException if the keys in the specified collection are not comparable, or are not mutually comparable. NullPointerException if the specified collection is null.
Parameters: s sorted set whose elements will comprise the new set.
Throws: NullPointerException if the specified sorted set is null.
Parameters: o element to be added to this set.
Returns: true if the set did not already contain the specified element.
Throws: ClassCastException if the specified object cannot be compared with the elements currently in the set.
Parameters: c elements to be added
Returns: 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. NullPointerException of the specified collection is null.
Returns: a shallow copy of this set.
Returns: the comparator used to order this sorted set, or null if this tree set uses its elements natural ordering.
Parameters: o the object to be checked for containment in this set.
Returns: true if this set contains the specified element.
Throws: ClassCastException if the specified object cannot be compared with the elements currently in the set.
Returns: the first (lowest) element currently in this sorted set.
Throws: NoSuchElementException sorted set is empty.
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");
Parameters: toElement high endpoint (exclusive) of the headSet.
Returns: a view of the portion of this set whose elements are strictly less than toElement.
Throws: 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.
Returns: true if this set contains no elements.
Returns: an iterator over the elements in this set.
Returns: the last (highest) element currently in this sorted set.
Throws: NoSuchElementException sorted set is empty.
Parameters: o object to be removed from this set, if present.
Returns: true if the set contained the specified element.
Throws: ClassCastException if the specified object cannot be compared with the elements currently in the set.
Returns: the number of elements in this set (its cardinality).
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);
Parameters: fromElement low endpoint (inclusive) of the subSet. toElement high endpoint (exclusive) of the subSet.
Returns: a view of the portion of this set whose elements range from fromElement, inclusive, to toElement, exclusive.
Throws: 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.
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");
Parameters: fromElement low endpoint (inclusive) of the tailSet.
Returns: a view of the portion of this set whose elements are greater than or equal to fromElement.
Throws: 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.