public
class
ConcurrentSkipListSet
extends AbstractSet<E>
implements
NavigableSet<E>,
Cloneable,
Serializable
java.lang.Object | |||
↳ | java.util.AbstractCollection<E> | ||
↳ | java.util.AbstractSet<E> | ||
↳ | java.util.concurrent.ConcurrentSkipListSet<E> |
A scalable concurrent 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 and spliterators are weakly consistent.
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.
Public constructors | |
---|---|
ConcurrentSkipListSet()
Constructs a new, empty set 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(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(SortedSet<E> s)
Constructs a new set containing the same elements and using the same ordering as the specified sorted set. |
Public methods | |
---|---|
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 |
void
|
clear()
Removes all of the elements from this set. |
ConcurrentSkipListSet<E>
|
clone()
Returns a shallow copy of this |
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 |
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 |
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 |
NavigableSet<E>
|
headSet(E toElement)
Returns a view of the portion of this set whose elements are strictly less than toElement. Equivalent to |
E
|
higher(E e)
Returns the least element in this set strictly greater than the
given element, or |
boolean
|
isEmpty()
Returns |
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 |
E
|
pollFirst()
Retrieves and removes the first (lowest) element,
or returns |
E
|
pollLast()
Retrieves and removes the last (highest) element,
or returns |
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. |
Spliterator<E>
|
spliterator()
Returns a |
NavigableSet<E>
|
subSet(E fromElement, boolean fromInclusive, E toElement, boolean toInclusive)
Returns a view of the portion of this set whose elements range from
|
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. Equivalent to |
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 |
NavigableSet<E>
|
tailSet(E fromElement)
Returns a view of the portion of this set whose elements are greater than or equal to fromElement. Equivalent to |
Inherited methods | |
---|---|
From
class
java.util.AbstractSet
| |
From
class
java.util.AbstractCollection
| |
From
class
java.lang.Object
| |
From
interface
java.util.Set
| |
From
interface
java.util.Collection
| |
From
interface
java.util.NavigableSet
| |
From
interface
java.lang.Iterable
| |
From
interface
java.util.SortedSet
|
ConcurrentSkipListSet ()
Constructs a new, empty set 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.
Parameters | |
---|---|
comparator |
Comparator :
the comparator that will be used to order this set.
If null , the natural
ordering of the elements will be used.
|
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.
Parameters | |
---|---|
c |
Collection :
The elements that will comprise the new set |
Throws | |
---|---|
ClassCastException |
if the elements in c are
not Comparable , or are not mutually comparable |
NullPointerException |
if the specified collection or any of its elements are null |
ConcurrentSkipListSet (SortedSet<E> s)
Constructs a new set containing the same elements and using the same ordering as the specified sorted set.
Parameters | |
---|---|
s |
SortedSet :
sorted set whose elements will comprise the new set |
Throws | |
---|---|
NullPointerException |
if the specified sorted set or any of its elements are null |
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.equals(e2)
.
If this set already contains the element, the call leaves the set
unchanged and returns false
.
Parameters | |
---|---|
e |
E :
element to be added to this set |
Returns | |
---|---|
boolean |
true if this set did not already contain the
specified element |
Throws | |
---|---|
ClassCastException |
if e cannot be compared
with the elements currently in this set |
NullPointerException |
if the specified element is null |
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.
Parameters | |
---|---|
e |
E :
the value to match |
Returns | |
---|---|
E |
the least element greater than or equal to e ,
or null if there is no such element |
Throws | |
---|---|
ClassCastException |
|
NullPointerException |
if the specified element is null |
ConcurrentSkipListSet<E> clone ()
Returns a shallow copy of this ConcurrentSkipListSet
instance. (The elements themselves are not cloned.)
Returns | |
---|---|
ConcurrentSkipListSet<E> |
a shallow copy of this set |
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.
Returns | |
---|---|
Comparator<? super E> |
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.
More formally, returns true
if and only if this set
contains an element e
such that o.equals(e)
.
Parameters | |
---|---|
o |
Object :
object to be checked for containment in this set |
Returns | |
---|---|
boolean |
true if this set contains the specified element |
Throws | |
---|---|
ClassCastException |
if the specified element cannot be compared with the elements currently in this set |
NullPointerException |
if the specified element is null |
Iterator<E> descendingIterator ()
Returns an iterator over the elements in this set in descending order.
Returns | |
---|---|
Iterator<E> |
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. The descending set is backed by this set, so changes to the set are reflected in the descending set, and vice-versa.
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
.
Returns | |
---|---|
NavigableSet<E> |
a reverse order view of this set |
boolean equals (Object o)
Compares the specified object with this set for equality. Returns
true
if the specified object is also a set, the two sets
have the same size, and every member of the specified set is
contained in this set (or equivalently, every member of this set is
contained in the specified set). This definition ensures that the
equals method works properly across different implementations of the
set interface.
Parameters | |
---|---|
o |
Object :
the object to be compared for equality with this set |
Returns | |
---|---|
boolean |
true if the specified object is equal to this set
|
E first ()
Returns the first (lowest) element currently in this set.
Returns | |
---|---|
E |
the first (lowest) element currently in this set |
Throws | |
---|---|
NoSuchElementException |
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.
Parameters | |
---|---|
e |
E :
the value to match |
Returns | |
---|---|
E |
the greatest element less than or equal to e ,
or null if there is no such element |
Throws | |
---|---|
ClassCastException |
|
NullPointerException |
if the specified element is null |
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
. 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.
Parameters | |
---|---|
toElement |
E :
high endpoint of the returned set |
inclusive |
boolean :
true if the high endpoint
is to be included in the returned view |
Returns | |
---|---|
NavigableSet<E> |
a view of the portion of this set whose elements are less than
(or equal to, if inclusive is true) toElement |
Throws | |
---|---|
ClassCastException |
|
NullPointerException |
if toElement is null |
IllegalArgumentException |
NavigableSet<E> headSet (E toElement)
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)
.
Parameters | |
---|---|
toElement |
E :
high endpoint (exclusive) of the returned set |
Returns | |
---|---|
NavigableSet<E> |
a view of the portion of this set whose elements are strictly less than toElement |
Throws | |
---|---|
ClassCastException |
|
NullPointerException |
if toElement is null |
IllegalArgumentException |
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.
Parameters | |
---|---|
e |
E :
the value to match |
Returns | |
---|---|
E |
the least element greater than e ,
or null if there is no such element |
Throws | |
---|---|
ClassCastException |
|
NullPointerException |
if the specified element is null |
boolean isEmpty ()
Returns true
if this set contains no elements.
Returns | |
---|---|
boolean |
true if this set contains no elements
|
Iterator<E> iterator ()
Returns an iterator over the elements in this set in ascending order.
Returns | |
---|---|
Iterator<E> |
an iterator over the elements in this set in ascending order |
E last ()
Returns the last (highest) element currently in this set.
Returns | |
---|---|
E |
the last (highest) element currently in this set |
Throws | |
---|---|
NoSuchElementException |
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.
Parameters | |
---|---|
e |
E :
the value to match |
Returns | |
---|---|
E |
the greatest element less than e ,
or null if there is no such element |
Throws | |
---|---|
ClassCastException |
|
NullPointerException |
if the specified element is null |
E pollFirst ()
Retrieves and removes the first (lowest) element,
or returns null
if this set is empty.
Returns | |
---|---|
E |
the first element, or null if this set is empty
|
E pollLast ()
Retrieves and removes the last (highest) element,
or returns null
if this set is empty.
Returns | |
---|---|
E |
the last element, or null if this set is empty
|
boolean remove (Object o)
Removes the specified element from this set if it is present.
More formally, removes an element e
such that
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.)
Parameters | |
---|---|
o |
Object :
object to be removed from this set, if present |
Returns | |
---|---|
boolean |
true if this set contained the specified element |
Throws | |
---|---|
ClassCastException |
if o cannot be compared
with the elements currently in this set |
NullPointerException |
if the specified element is null |
boolean removeAll (Collection<?> c)
Removes from this set all of its elements that are contained in the specified collection. If the specified collection is also a set, this operation effectively modifies this set so that its value is the asymmetric set difference of the two sets.
Parameters | |
---|---|
c |
Collection :
collection containing elements to be removed from this set |
Returns | |
---|---|
boolean |
true if this set changed as a result of the call |
Throws | |
---|---|
ClassCastException |
if the class of an element of this set is incompatible with the specified collection (optional) |
NullPointerException |
if the specified collection or any of its elements are null |
int size ()
Returns the number of elements in this set. If this set
contains more than Integer.MAX_VALUE
elements, it
returns Integer.MAX_VALUE
.
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.
Returns | |
---|---|
int |
the number of elements in this set |
Spliterator<E> spliterator ()
Returns a Spliterator
over the elements in this set.
The Spliterator
reports CONCURRENT
,
NONNULL
, DISTINCT
,
SORTED
and ORDERED
, with an
encounter order that is ascending order. Overriding implementations
should document the reporting of additional characteristic values.
The spliterator's comparator (see
getComparator()
) is null
if
the set's comparator (see comparator()
) is null
.
Otherwise, the spliterator's comparator is the same as or imposes the
same total ordering as the set's comparator.
Returns | |
---|---|
Spliterator<E> |
a Spliterator over the 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
. 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.
Parameters | |
---|---|
fromElement |
E :
low endpoint of the returned set |
fromInclusive |
boolean :
true if the low endpoint
is to be included in the returned view |
toElement |
E :
high endpoint of the returned set |
toInclusive |
boolean :
true if the high endpoint
is to be included in the returned view |
Returns | |
---|---|
NavigableSet<E> |
a view of the portion of this set whose elements range from
fromElement , inclusive, to toElement , exclusive |
Throws | |
---|---|
ClassCastException |
|
NullPointerException |
if fromElement or
toElement is null |
IllegalArgumentException |
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. (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)
.
Parameters | |
---|---|
fromElement |
E :
low endpoint (inclusive) of the returned set |
toElement |
E :
high endpoint (exclusive) of the returned set |
Returns | |
---|---|
NavigableSet<E> |
a view of the portion of this set whose elements range from fromElement, inclusive, to toElement, exclusive |
Throws | |
---|---|
ClassCastException |
|
NullPointerException |
if fromElement or
toElement is null |
IllegalArgumentException |
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
.
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.
Parameters | |
---|---|
fromElement |
E :
low endpoint of the returned set |
inclusive |
boolean :
true if the low endpoint
is to be included in the returned view |
Returns | |
---|---|
NavigableSet<E> |
a view of the portion of this set whose elements are greater
than or equal to fromElement |
Throws | |
---|---|
ClassCastException |
|
NullPointerException |
if fromElement is null |
IllegalArgumentException |
NavigableSet<E> tailSet (E fromElement)
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)
.
Parameters | |
---|---|
fromElement |
E :
low endpoint (inclusive) of the returned set |
Returns | |
---|---|
NavigableSet<E> |
a view of the portion of this set whose elements are greater than or equal to fromElement |
Throws | |
---|---|
ClassCastException |
|
NullPointerException |
if fromElement is null |
IllegalArgumentException |