E - the type of elements maintained by this set
public class TreeSet<E> extends AbstractSet<E> implements NavigableSet <E>, Cloneable , Serializable
NavigableSet implementation based on a
TreeMap. The elements are ordered using their
natural ordering, or by a
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 tree 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.synchronizedSortedSet 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,
TreeMap,
Serialized Form
| Constructor and Description |
|---|
TreeSet()
Constructs a new, empty tree set, sorted according to the natural ordering of its elements.
|
TreeSet(Collection
Constructs a new tree set containing the elements in the specified collection, sorted according to the
natural ordering of its elements.
|
TreeSet(Comparator
Constructs a new, empty tree set, sorted according to the specified comparator.
|
TreeSet(SortedSet
Constructs a new tree set containing the same elements and using the same ordering as the specified sorted set.
|
| Modifier and Type | Method and Description |
|---|---|
boolean |
add(E e)
Adds the specified element to this set if it is not already present.
|
boolean |
addAll(Collection
Adds all of the elements in the specified collection to this set.
|
E |
ceiling(E e)
Returns the least element in this set greater than or equal to the given element, or
null if there is no such element.
|
void |
clear()
Removes all of the elements from this set.
|
Object |
clone()
Returns a shallow copy of this
TreeSet instance.
|
Comparator |
comparator()
Returns the comparator used to order the elements in this set, or
null if this set uses the
natural ordering of its elements.
|
boolean |
contains(Object
Returns
true if this set contains the specified element.
|
Iterator |
descendingIterator()
Returns an iterator over the elements in this set in descending order.
|
NavigableSet |
descendingSet()
Returns a reverse order view of the elements contained in this set.
|
E |
first()
Returns the first (lowest) element currently in this set.
|
E |
floor(E e)
Returns the greatest element in this set less than or equal to the given element, or
null if there is no such element.
|
SortedSet |
headSet(E toElement)
Returns a view of the portion of this set whose elements are strictly less than
toElement.
|
NavigableSet |
headSet(E toElement, boolean inclusive)
Returns a view of the portion of this set whose elements are less than (or equal to, if
inclusive is true)
toElement.
|
E |
higher(E e)
Returns the least element in this set strictly greater than the given element, or
null if there is no such element.
|
boolean |
isEmpty()
Returns
true if this set contains no elements.
|
Iterator |
iterator()
Returns an iterator over the elements in this set in ascending order.
|
E |
last()
Returns the last (highest) element currently in this set.
|
E |
lower(E e)
Returns the greatest element in this set strictly less than the given element, or
null if there is no such element.
|
E |
pollFirst()
Retrieves and removes the first (lowest) element, or returns
null if this set is empty.
|
E |
pollLast()
Retrieves and removes the last (highest) element, or returns
null if this set is empty.
|
boolean |
remove(Object
Removes the specified element from this set if it is present.
|
int |
size()
Returns the number of elements in this set (its cardinality).
|
Spliterator |
spliterator()
Creates a
late-binding and
fail-fast
Spliterator over the elements in this set.
|
NavigableSet |
subSet(E fromElement, boolean fromInclusive, E toElement, boolean toInclusive)
Returns a view of the portion of this set whose elements range from
fromElement to
toElement.
|
SortedSet |
subSet(E fromElement, E toElement)
Returns a view of the portion of this set whose elements range from
fromElement, inclusive, to
toElement, exclusive.
|
SortedSet |
tailSet(E fromElement)
Returns a view of the portion of this set whose elements are greater than or equal to
fromElement.
|
NavigableSet |
tailSet(E fromElement, boolean inclusive)
Returns a view of the portion of this set whose elements are greater than (or equal to, if
inclusive is true)
fromElement.
|
equals, hashCode, removeAllcontainsAll, retainAll, toArray, toArray, toStringfinalize, getClass, notify, notifyAll, wait, wait, waitcontainsAll, equals, hashCode, removeAll, retainAll, toArray, toArrayparallelStream, removeIf, streampublic TreeSet()
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 call will throw a
ClassCastException.
public TreeSet(Comparator<? super E> 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 call will throw a
ClassCastException.
comparator - the comparator that will be used to order this set. If
null, the
natural ordering of the elements will be used.
public TreeSet(Collection<? extends E> c)
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.
c - collection whose elements will comprise the new set
ClassCastException - if the elements in
c 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
public Iterator<E> iterator()
iterator in interface
Iterable<E>
iterator in interface
Collection<E>
iterator in interface
NavigableSet<E>
iterator in interface
Set<E>
iterator in class
AbstractCollection<E>
public Iterator<E> descendingIterator()
descendingIterator in interface
NavigableSet<E>
public NavigableSet<E> descendingSet()
NavigableSet
remove operation), the results of the iteration are undefined.
The returned set has an ordering equivalent to Collections.reverseOrder(comparator()). The expression s.descendingSet().descendingSet() returns a view of s essentially equivalent to s.
descendingSet in interface
NavigableSet<E>
public int size()
size in interface
Collection<E>
size in interface
Set<E>
size in class
AbstractCollection<E>
public boolean isEmpty()
true if this set contains no elements.
isEmpty in interface
Collection<E>
isEmpty in interface
Set<E>
isEmpty in class
AbstractCollection<E>
true if this set contains no elements
public boolean contains(Objecto)
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)).
contains in interface
Collection<E>
contains in interface
Set<E>
contains in class
AbstractCollection<E>
o - object to be checked for containment in this set
true if this set contains the specified element
ClassCastException - if the specified object cannot be compared with the elements currently in the set
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)
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.
add in interface
Collection<E>
add in interface
Set<E>
add in class
AbstractCollection<E>
e - element to be added to this set
true if this set did not already contain the specified element
ClassCastException - if the specified object cannot be compared with the elements currently in this set
NullPointerException - if the specified element is null and this set uses natural ordering, or its comparator does not permit null elements
public boolean remove(Objecto)
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.)
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
true if this set contained the specified element
ClassCastException - if the specified object cannot be compared with the elements currently in this set
NullPointerException - if the specified element is null and this set uses natural ordering, or its comparator does not permit null elements
public void clear()
public boolean addAll(Collection<? extends E> c)
addAll in interface
Collection<E>
addAll in interface
Set<E>
addAll in class
AbstractCollection<E>
c - collection containing elements to be added to this set
true if this set changed as a result of the call
ClassCastException - if the elements provided cannot be compared with the elements currently in the set
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
AbstractCollection.add(Object)
public NavigableSet<E> subSet(E fromElement, boolean fromInclusive, E toElement, boolean toInclusive)
NavigableSet
fromElement to
toElement. If
fromElement and
toElement are equal, the returned set is empty unless
fromInclusive and
toInclusive are both true. The returned set is backed by this set, so changes in the returned set are reflected in this set, and vice-versa. The returned set supports all optional set operations that this set supports.
The returned set will throw an IllegalArgumentException on an attempt to insert an element outside its range.
subSet in interface
NavigableSet<E>
fromElement - low endpoint of the returned set
fromInclusive -
true if the low endpoint is to be included in the returned view
toElement - high endpoint of the returned set
toInclusive -
true if the high endpoint is to be included in the returned view
fromElement, inclusive, to
toElement, exclusive
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). Implementations may, but are not required to, throw this exception if
fromElement or
toElement cannot be compared to elements currently in the set.
NullPointerException - if
fromElement or
toElement is null and this set uses natural ordering, or its comparator does not permit null elements
IllegalArgumentException - if
fromElement is greater than
toElement; or if this set itself has a restricted range, and
fromElement or
toElement lies outside the bounds of the range.
public NavigableSet<E> headSet(E toElement, boolean inclusive)
NavigableSet
inclusive is true)
toElement. The returned set is backed by this set, so changes in the returned set are reflected in this set, and vice-versa. The returned set supports all optional set operations that this set supports.
The returned set will throw an IllegalArgumentException on an attempt to insert an element outside its range.
headSet in interface
NavigableSet<E>
toElement - high endpoint of the returned set
inclusive -
true if the high endpoint is to be included in the returned view
inclusive is true)
toElement
ClassCastException - if
toElement is not compatible with this set's comparator (or, if the set has no comparator, if
toElement does not implement
Comparable). Implementations may, but are not required to, throw this exception if
toElement cannot be compared to elements currently in the set.
NullPointerException - if
toElement is null and this set uses natural ordering, or its comparator does not permit null elements
IllegalArgumentException - if this set itself has a restricted range, and
toElement lies outside the bounds of the range
public NavigableSet<E> tailSet(E fromElement, boolean inclusive)
NavigableSet
inclusive is true)
fromElement. The returned set is backed by this set, so changes in the returned set are reflected in this set, and vice-versa. The returned set supports all optional set operations that this set supports.
The returned set will throw an IllegalArgumentException on an attempt to insert an element outside its range.
tailSet in interface
NavigableSet<E>
fromElement - low endpoint of the returned set
inclusive -
true if the low endpoint is to be included in the returned view
fromElement
ClassCastException - if
fromElement is not compatible with this set's comparator (or, if the set has no comparator, if
fromElement does not implement
Comparable). Implementations may, but are not required to, throw this exception if
fromElement cannot be compared to elements currently in the set.
NullPointerException - if
fromElement is null and this set uses natural ordering, or its comparator does not permit null elements
IllegalArgumentException - if this set itself has a restricted range, and
fromElement lies outside the bounds of the range
public SortedSet<E> subSet(E fromElement, E toElement)
NavigableSet
The returned set will throw an IllegalArgumentException on an attempt to insert an element outside its range.
Equivalent to subSet(fromElement, true, toElement, false).
subSet in interface
NavigableSet<E>
subSet in interface
SortedSet<E>
fromElement - low endpoint (inclusive) of the returned set
toElement - high endpoint (exclusive) of the returned set
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). Implementations may, but are not required to, throw this exception if
fromElement or
toElement cannot be compared to elements currently in the set.
NullPointerException - if
fromElement or
toElement is null and this set uses natural ordering, or its comparator does not permit null elements
IllegalArgumentException - if
fromElement is greater than
toElement; or if this set itself has a restricted range, and
fromElement or
toElement lies outside the bounds of the range
public SortedSet<E> headSet(E toElement)
NavigableSet
The returned set will throw an IllegalArgumentException on an attempt to insert an element outside its range.
Equivalent to headSet(toElement, false).
headSet in interface
NavigableSet<E>
headSet in interface
SortedSet<E>
toElement - high endpoint (exclusive) of the returned set
ClassCastException - if
toElement is not compatible with this set's comparator (or, if the set has no comparator, if
toElement does not implement
Comparable). Implementations may, but are not required to, throw this exception if
toElement cannot be compared to elements currently in the set.
NullPointerException - if
toElement is null and this set uses natural ordering, or its comparator does not permit null elements
IllegalArgumentException - if this set itself has a restricted range, and
toElement lies outside the bounds of the range
public SortedSet<E> tailSet(E fromElement)
NavigableSet
The returned set will throw an IllegalArgumentException on an attempt to insert an element outside its range.
Equivalent to tailSet(fromElement, true).
tailSet in interface
NavigableSet<E>
tailSet in interface
SortedSet<E>
fromElement - low endpoint (inclusive) of the returned set
ClassCastException - if
fromElement is not compatible with this set's comparator (or, if the set has no comparator, if
fromElement does not implement
Comparable). Implementations may, but are not required to, throw this exception if
fromElement cannot be compared to elements currently in the set.
NullPointerException - if
fromElement is null and this set uses natural ordering, or its comparator does not permit null elements
IllegalArgumentException - if this set itself has a restricted range, and
fromElement lies outside the bounds of the range
public Comparator<? super E> comparator()
SortedSet
comparator in interface
SortedSet<E>
public E first()
SortedSet
first in interface
SortedSet<E>
NoSuchElementException - if this set is empty
public E last()
SortedSet
last in interface
SortedSet<E>
NoSuchElementException - if this set is empty
public E lower(E e)
NavigableSet
null if there is no such element.
lower in interface
NavigableSet<E>
e - the value to match
e, or
null if there is no such element
ClassCastException - if the specified element cannot be compared with the elements currently in the set
NullPointerException - if the specified element is null and this set uses natural ordering, or its comparator does not permit null elements
public E floor(E e)
NavigableSet
null if there is no such element.
floor in interface
NavigableSet<E>
e - the value to match
e, or
null if there is no such element
ClassCastException - if the specified element cannot be compared with the elements currently in the set
NullPointerException - if the specified element is null and this set uses natural ordering, or its comparator does not permit null elements
public E ceiling(E e)
NavigableSet
null if there is no such element.
ceiling in interface
NavigableSet<E>
e - the value to match
e, or
null if there is no such element
ClassCastException - if the specified element cannot be compared with the elements currently in the set
NullPointerException - if the specified element is null and this set uses natural ordering, or its comparator does not permit null elements
public E higher(E e)
NavigableSet
null if there is no such element.
higher in interface
NavigableSet<E>
e - the value to match
e, or
null if there is no such element
ClassCastException - if the specified element cannot be compared with the elements currently in the set
NullPointerException - if the specified element is null and this set uses natural ordering, or its comparator does not permit null elements
public E pollFirst()
NavigableSet
null if this set is empty.
pollFirst in interface
NavigableSet<E>
null if this set is empty
public E pollLast()
NavigableSet
null if this set is empty.
pollLast in interface
NavigableSet<E>
null if this set is empty
public Objectclone()
TreeSet instance. (The elements themselves are not cloned.)
public Spliterator<E> spliterator()
Spliterator over the elements in this set.
The Spliterator reports Spliterator, Spliterator, Spliterator, and Spliterator. Overriding implementations should document the reporting of additional characteristic values.
The spliterator's comparator (see Spliterator) is null if the tree set's comparator (see comparator()) is null. Otherwise, the spliterator's comparator is the same as or imposes the same total ordering as the tree set's comparator.
spliterator in interface
Iterable<E>
spliterator in interface
Collection<E>
spliterator in interface
Set<E>
spliterator in interface
SortedSet<E>
Spliterator over the elements in this set