E - the type of elements maintained by this setpublic class ConcurrentSkipListSet<E> extends AbstractSet<E> implements NavigableSet<E>, Cloneable, Serializable
NavigableSet implementation based on
a ConcurrentSkipListMap. The elements of the set are kept
sorted according to their natural ordering,
or by a Comparator provided at set creation time, depending
on which constructor is used.
This implementation provides expected average log(n) time
cost for the contains, add, and remove
operations and their variants. Insertion, removal, and access
operations safely execute concurrently by multiple threads.
Iterators are weakly consistent, returning elements
reflecting the state of the set at some point at or since the
creation of the iterator. They do not throw ConcurrentModificationException, and may proceed concurrently with
other operations. Ascending ordered views and their iterators are
faster than descending ones.
Beware that, unlike in most collections, the size method is not a constant-time operation. Because of the asynchronous nature of these sets, determining the current number of elements requires a traversal of the elements, and so may report inaccurate results if this collection is modified during traversal. Additionally, the bulk operations addAll, removeAll, retainAll, containsAll, equals, and toArray are not guaranteed to be performed atomically. For example, an iterator operating concurrently with an addAll operation might view only some of the added elements.
This class and its iterators implement all of the
optional methods of the Set and Iterator
interfaces. Like most other concurrent collection implementations,
this class does not permit the use of null elements,
because null arguments and return values cannot be reliably
distinguished from the absence of elements.
This class is a member of the Java Collections Framework.
| Constructor and Description |
|---|
ConcurrentSkipListSet()
Constructs a new, empty set that orders its elements according to
their natural ordering.
|
ConcurrentSkipListSet(Collection<? extends E> c)
Constructs a new set containing the elements in the specified
collection, that orders its elements according to their
natural ordering.
|
ConcurrentSkipListSet(Comparator<? super E> comparator)
Constructs a new, empty set that orders its elements according to
the specified comparator.
|
ConcurrentSkipListSet(SortedSet<E> s)
Constructs a new 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.
|
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.
|
ConcurrentSkipListSet<E> |
clone()
Returns a shallow copy of this ConcurrentSkipListSet
instance.
|
Comparator<? super E> |
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 o)
Returns true if this set contains the specified element.
|
Iterator<E> |
descendingIterator()
Returns an iterator over the elements in this set in descending order.
|
NavigableSet<E> |
descendingSet()
Returns a reverse order view of the elements contained in this set.
|
boolean |
equals(Object o)
Compares the specified object with this set for equality.
|
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. |
NavigableSet<E> |
headSet(E toElement)
Returns a view of the portion of this set whose elements are
strictly less than toElement.
|
NavigableSet<E> |
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<E> |
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 o)
Removes the specified element from this set if it is present.
|
boolean |
removeAll(Collection<?> c)
Removes from this set all of its elements that are contained in
the specified collection.
|
int |
size()
Returns the number of elements in this set.
|
NavigableSet<E> |
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. |
NavigableSet<E> |
subSet(E fromElement,
E toElement)
Returns a view of the portion of this set whose elements range
from fromElement, inclusive, to toElement,
exclusive.
|
NavigableSet<E> |
tailSet(E fromElement)
Returns a view of the portion of this set whose elements are
greater than or equal to fromElement.
|
NavigableSet<E> |
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. |
hashCodeaddAll, containsAll, retainAll, toArray, toArray, toStringpublic ConcurrentSkipListSet()
public ConcurrentSkipListSet(Comparator<? super E> comparator)
comparator - the comparator that will be used to order this set.
If null, the natural
ordering of the elements will be used.public ConcurrentSkipListSet(Collection<? extends E> c)
c - The elements that will comprise the new setClassCastException - if the elements in c are
not Comparable, or are not mutually comparableNullPointerException - if the specified collection or any
of its elements are nullpublic ConcurrentSkipListSet(SortedSet<E> s)
s - sorted set whose elements will comprise the new setNullPointerException - if the specified sorted set or any
of its elements are nullpublic ConcurrentSkipListSet<E> clone()
public int size()
Beware that, unlike in most collections, this method is NOT a constant-time operation. Because of the asynchronous nature of these sets, determining the current number of elements requires traversing them all to count them. Additionally, it is possible for the size to change during execution of this method, in which case the returned result will be inaccurate. Thus, this method is typically not very useful in concurrent applications.
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 - object to be checked for containment in this setClassCastException - if the specified element cannot be
compared with the elements currently in this setNullPointerException - if the specified element is nullpublic boolean add(E e)
add in interface Collection<E>add in interface Set<E>add in class AbstractCollection<E>e - element to be added to this setClassCastException - if e cannot be compared
with the elements currently in this setNullPointerException - if the specified element is nullpublic 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 presentClassCastException - if o cannot be compared
with the elements currently in this setNullPointerException - if the specified element is nullpublic void clear()
clear in interface Collection<E>clear in interface Set<E>clear in class AbstractCollection<E>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 boolean equals(Object o)
equals in interface Collection<E>equals in interface Set<E>equals in class AbstractSet<E>o - the object to be compared for equality with this setObject.hashCode(),
HashMappublic boolean removeAll(Collection<?> c)
removeAll in interface Collection<E>removeAll in interface Set<E>removeAll in class AbstractSet<E>c - collection containing elements to be removed from this setClassCastException - if the types of one or more elements in this
set are incompatible with the specified collectionNullPointerException - if the specified collection or any
of its elements are nullAbstractCollection.remove(Object),
AbstractCollection.contains(Object)public E lower(E e)
NavigableSetnull 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 nullpublic E floor(E e)
NavigableSetnull 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 nullpublic E ceiling(E e)
NavigableSetnull 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 nullpublic E higher(E e)
NavigableSetnull 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 nullpublic E pollFirst()
NavigableSetnull if this set is empty.pollFirst in interface NavigableSet<E>null if this set is emptypublic E pollLast()
NavigableSetnull if this set is empty.pollLast in interface NavigableSet<E>null if this set is emptypublic Comparator<? super E> comparator()
SortedSetcomparator in interface SortedSet<E>public E first()
SortedSetfirst in interface SortedSet<E>NoSuchElementException - if this set is emptypublic E last()
SortedSetlast in interface SortedSet<E>NoSuchElementException - if this set is emptypublic NavigableSet<E> subSet(E fromElement, boolean fromInclusive, E toElement, boolean toInclusive)
NavigableSetfromElement 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 nullIllegalArgumentException - 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)
NavigableSetinclusive 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) toElementClassCastException - 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 nullIllegalArgumentException - if this set itself has a
restricted range, and toElement lies outside the
bounds of the rangepublic NavigableSet<E> tailSet(E fromElement, boolean inclusive)
NavigableSetinclusive 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 viewfromElementClassCastException - 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 nullIllegalArgumentException - if this set itself has a
restricted range, and fromElement lies outside the
bounds of the rangepublic NavigableSet<E> subSet(E fromElement, E toElement)
NavigableSetThe 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 setClassCastException - 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 nullIllegalArgumentException - 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 NavigableSet<E> headSet(E toElement)
NavigableSetThe 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 setClassCastException - 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 nullIllegalArgumentException - if this set itself has a
restricted range, and toElement lies outside the
bounds of the range
napublic NavigableSet<E> tailSet(E fromElement)
NavigableSetThe 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 setClassCastException - 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 nullIllegalArgumentException - if this set itself has a
restricted range, and fromElement lies outside the
bounds of the rangepublic NavigableSet<E> descendingSet()
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>