E - the type of elements maintained by this setpublic class TreeSet<E> extends AbstractSet<E> implements NavigableSet<E>, Cloneable, Serializable
A 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 Formpublic TreeSet()
Constructs a new, empty tree set, sorted according to the natural ordering of its elements. All elements inserted into the set must implement the 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)
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 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)
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 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 setClassCastException - if the elements in c are not Comparable, or are not mutually comparableNullPointerException - if the specified collection is nullpublic TreeSet(SortedSet<E> s)
Constructs a new tree set containing the same elements and using the same ordering as the specified sorted set.
s - sorted set whose elements will comprise the new setNullPointerException - if the specified sorted set is nullpublic Iterator<E> iterator()
Returns an iterator over the elements in this set in ascending order.
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()
Returns an iterator over the elements in this set in descending order.
descendingIterator in interface NavigableSet<E>
public NavigableSet<E> descendingSet()
Description copied from interface: NavigableSet
Returns a reverse order view of the elements contained in this set. The descending set is backed by this set, so changes to the set are reflected in the descending set, and vice-versa. If either set is modified while an iteration over either set is in progress (except through the iterator's own remove operation), the results of the iteration are undefined.
The returned set has an ordering equivalent to Collections.reverseOrder(comparator())s.descendingSet().descendingSet() returns a view of s essentially equivalent to s.
descendingSet in interface NavigableSet<E>
public int size()
Returns the number of elements in this set (its cardinality).
size in interface Collection<E>
size in interface Set<E>
size in class AbstractCollection<E>
public boolean isEmpty()
Returns 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 elementspublic boolean contains(Object o)
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)).
contains in interface Collection<E>
contains in interface Set<E>
contains in class AbstractCollection<E>
o - object to be checked for containment in this settrue if this set contains the specified elementClassCastException - if the specified object cannot be compared with the elements currently in the setNullPointerException - if the specified element is null and this set uses natural ordering, or its comparator does not permit null elementspublic boolean add(E e)
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.
add in interface Collection<E>
add in interface Set<E>
add in class AbstractCollection<E>
e - element to be added to this settrue if this set did not already contain the specified elementClassCastException - if the specified object cannot be compared with the elements currently in this setNullPointerException - if the specified element is null and this set uses natural ordering, or its comparator does not permit null elementspublic boolean remove(Object o)
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.)
remove in interface Collection<E>
remove in interface Set<E>
remove in class AbstractCollection<E>
o - object to be removed from this set, if presenttrue if this set contained the specified elementClassCastException - if the specified object cannot be compared with the elements currently in this setNullPointerException - if the specified element is null and this set uses natural ordering, or its comparator does not permit null elementspublic void clear()
Removes all of the elements from this set. The set will be empty after this call returns.
clear in interface Collection<E>
clear in interface Set<E>
clear in class AbstractCollection<E>
public boolean addAll(Collection<? extends E> c)
Adds all of the elements in the specified collection to this set.
addAll in interface Collection<E>
addAll in interface Set<E>
addAll in class AbstractCollection<E>
c - collection containing elements to be added to this settrue if this set changed as a result of the callClassCastException - if the elements provided cannot be compared with the elements currently in the setNullPointerException - 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 elementsAbstractCollection.add(Object)public NavigableSet<E> subSet(E fromElement,
boolean fromInclusive,
E toElement,
boolean toInclusive) Description copied from interface: NavigableSet
Returns a view of the portion of this set whose elements range from 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 setfromInclusive - true if the low endpoint is to be included in the returned viewtoElement - high endpoint of the returned settoInclusive - true if the high endpoint is to be included in the returned viewfromElement, inclusive, to toElement, exclusiveClassCastException - 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 elementsIllegalArgumentException - 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) Description copied from interface: NavigableSet
Returns a view of the portion of this set whose elements are less than (or equal to, if 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 setinclusive - true if the high endpoint is to be included in the returned viewinclusive 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 elementsIllegalArgumentException - if this set itself has a restricted range, and toElement lies outside the bounds of the rangepublic NavigableSet<E> tailSet(E fromElement,
boolean inclusive) Description copied from interface: NavigableSet
Returns a view of the portion of this set whose elements are greater than (or equal to, if 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 setinclusive - true if the low endpoint is to be included in the returned viewfromElement
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 elementsIllegalArgumentException - if this set itself has a restricted range, and fromElement lies outside the bounds of the rangepublic SortedSet<E> subSet(E fromElement,
E toElement) Description copied from interface: NavigableSet
Returns a view of the portion of this set whose elements range from fromElement, inclusive, to toElement, exclusive. (If fromElement and toElement are equal, the returned set is empty.) 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.
Equivalent to subSet(fromElement, true, toElement, false).
subSet in interface NavigableSet<E>
subSet in interface SortedSet<E>
fromElement - low endpoint (inclusive) of the returned settoElement - high endpoint (exclusive) of the returned setfromElement, inclusive, to toElement, exclusiveClassCastException - 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 elementsIllegalArgumentException - 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 rangepublic SortedSet<E> headSet(E toElement)
Description copied from interface: NavigableSet
Returns a view of the portion of this set whose elements are strictly less than 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.
Equivalent to headSet(toElement, false).
headSet in interface NavigableSet<E>
headSet in interface SortedSet<E>
toElement - high endpoint (exclusive) of the returned settoElement
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 elementsIllegalArgumentException - if this set itself has a restricted range, and toElement lies outside the bounds of the rangepublic SortedSet<E> tailSet(E fromElement)
Description copied from interface: NavigableSet
Returns a view of the portion of this set whose elements are greater than or equal to 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.
Equivalent to tailSet(fromElement, true).
tailSet in interface NavigableSet<E>
tailSet in interface SortedSet<E>
fromElement - low endpoint (inclusive) of the returned setfromElement
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 elementsIllegalArgumentException - if this set itself has a restricted range, and fromElement lies outside the bounds of the rangepublic Comparator<? super E> comparator()
Description copied from interface: SortedSet
Returns the comparator used to order the elements in this set, or null if this set uses the natural ordering of its elements.
comparator in interface SortedSet<E>
null if this set uses the natural ordering of its elementspublic E first()
Description copied from interface: SortedSet
Returns the first (lowest) element currently in this set.
first in interface SortedSet<E>
NoSuchElementException - if this set is emptypublic E last()
Description copied from interface: SortedSet
Returns the last (highest) element currently in this set.
last in interface SortedSet<E>
NoSuchElementException - if this set is emptypublic E lower(E e)
Description copied from interface: NavigableSet
Returns the greatest element in this set strictly less than the given element, or null if there is no such element.
lower in interface NavigableSet<E>
e - the value to matche, or null if there is no such elementClassCastException - if the specified element cannot be compared with the elements currently in the setNullPointerException - if the specified element is null and this set uses natural ordering, or its comparator does not permit null elementspublic E floor(E e)
Description copied from interface: NavigableSet
Returns the greatest element in this set less than or equal to the given element, or null if there is no such element.
floor in interface NavigableSet<E>
e - the value to matche, or null if there is no such elementClassCastException - if the specified element cannot be compared with the elements currently in the setNullPointerException - if the specified element is null and this set uses natural ordering, or its comparator does not permit null elementspublic E ceiling(E e)
Description copied from interface: NavigableSet
Returns the least element in this set greater than or equal to the given element, or null if there is no such element.
ceiling in interface NavigableSet<E>
e - the value to matche, or null if there is no such elementClassCastException - if the specified element cannot be compared with the elements currently in the setNullPointerException - if the specified element is null and this set uses natural ordering, or its comparator does not permit null elementspublic E higher(E e)
Description copied from interface: NavigableSet
Returns the least element in this set strictly greater than the given element, or null if there is no such element.
higher in interface NavigableSet<E>
e - the value to matche, or null if there is no such elementClassCastException - if the specified element cannot be compared with the elements currently in the setNullPointerException - if the specified element is null and this set uses natural ordering, or its comparator does not permit null elementspublic E pollFirst()
Description copied from interface: NavigableSet
Retrieves and removes the first (lowest) element, or returns null if this set is empty.
pollFirst in interface NavigableSet<E>
null if this set is emptypublic E pollLast()
Description copied from interface: NavigableSet
Retrieves and removes the last (highest) element, or returns null if this set is empty.
pollLast in interface NavigableSet<E>
null if this set is emptypublic Object clone()
Returns a shallow copy of this TreeSet instance. (The elements themselves are not cloned.)
public Spliterator<E> spliterator()
Creates a late-binding and fail-fast Spliterator over the elements in this set.
The Spliterator reports Spliterator.SIZED, Spliterator.DISTINCT, Spliterator.SORTED, and Spliterator.ORDERED. Overriding implementations should document the reporting of additional characteristic values.
The spliterator's comparator (see Spliterator.getComparator()) 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
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