edu.emory.mathcs.backport.java.util.concurrent
public class ConcurrentSkipListSet extends AbstractSet implements NavigableSet, java.lang.Cloneable, java.io.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. Additionally, the bulk operations addAll, removeAll, retainAll, and containsAll 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(java.util.Collection c)
Constructs a new set containing the elements in the specified
collection, that orders its elements according to their
natural ordering.
|
ConcurrentSkipListSet(java.util.Comparator comparator)
Constructs a new, empty set that orders its elements according to
the specified comparator.
|
ConcurrentSkipListSet(java.util.SortedSet 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(java.lang.Object e)
Adds the specified element to this set if it is not already present.
|
java.lang.Object |
ceiling(java.lang.Object 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.
|
java.lang.Object |
clone()
Returns a shallow copy of this ConcurrentSkipListSet
instance.
|
java.util.Comparator |
comparator() |
boolean |
contains(java.lang.Object o)
Returns true if this set contains the specified element.
|
java.util.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.
|
boolean |
equals(java.lang.Object o)
Compares the specified object with this set for equality.
|
java.lang.Object |
first() |
java.lang.Object |
floor(java.lang.Object e)
Returns the greatest element in this set less than or equal to
the given element, or
null if there is no such element. |
java.util.SortedSet |
headSet(java.lang.Object toElement) |
NavigableSet |
headSet(java.lang.Object 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 . |
java.lang.Object |
higher(java.lang.Object 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.
|
java.util.Iterator |
iterator()
Returns an iterator over the elements in this set in ascending order.
|
java.lang.Object |
last() |
java.lang.Object |
lower(java.lang.Object e)
Returns the greatest element in this set strictly less than the
given element, or
null if there is no such element. |
java.lang.Object |
pollFirst()
Retrieves and removes the first (lowest) element,
or returns
null if this set is empty. |
java.lang.Object |
pollLast()
Retrieves and removes the last (highest) element,
or returns
null if this set is empty. |
boolean |
remove(java.lang.Object o)
Removes the specified element from this set if it is present.
|
boolean |
removeAll(java.util.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 |
subSet(java.lang.Object fromElement,
boolean fromInclusive,
java.lang.Object toElement,
boolean toInclusive)
Returns a view of the portion of this set whose elements range from
fromElement to toElement . |
java.util.SortedSet |
subSet(java.lang.Object fromElement,
java.lang.Object toElement) |
java.util.SortedSet |
tailSet(java.lang.Object fromElement) |
NavigableSet |
tailSet(java.lang.Object 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 . |
toArray, toArray
public ConcurrentSkipListSet()
public ConcurrentSkipListSet(java.util.Comparator 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(java.util.Collection c)
c
- The elements that will comprise the new setjava.lang.ClassCastException
- if the elements in c are
not Comparable
, or are not mutually comparablejava.lang.NullPointerException
- if the specified collection or any
of its elements are nullpublic ConcurrentSkipListSet(java.util.SortedSet s)
s
- sorted set whose elements will comprise the new setjava.lang.NullPointerException
- if the specified sorted set or any
of its elements are nullpublic java.lang.Object clone()
clone
in class java.lang.Object
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 java.util.Collection
size
in interface java.util.Set
size
in class java.util.AbstractCollection
public boolean isEmpty()
isEmpty
in interface java.util.Collection
isEmpty
in interface java.util.Set
isEmpty
in class java.util.AbstractCollection
public boolean contains(java.lang.Object o)
contains
in interface java.util.Collection
contains
in interface java.util.Set
contains
in class java.util.AbstractCollection
o
- object to be checked for containment in this setjava.lang.ClassCastException
- if the specified element cannot be
compared with the elements currently in this setjava.lang.NullPointerException
- if the specified element is nullpublic boolean add(java.lang.Object e)
add
in interface java.util.Collection
add
in interface java.util.Set
add
in class java.util.AbstractCollection
e
- element to be added to this setjava.lang.ClassCastException
- if e cannot be compared
with the elements currently in this setjava.lang.NullPointerException
- if the specified element is nullpublic boolean remove(java.lang.Object o)
remove
in interface java.util.Collection
remove
in interface java.util.Set
remove
in class java.util.AbstractCollection
o
- object to be removed from this set, if presentjava.lang.ClassCastException
- if o cannot be compared
with the elements currently in this setjava.lang.NullPointerException
- if the specified element is nullpublic void clear()
clear
in interface java.util.Collection
clear
in interface java.util.Set
clear
in class java.util.AbstractCollection
public java.util.Iterator iterator()
iterator
in interface NavigableSet
iterator
in interface java.lang.Iterable
iterator
in interface java.util.Collection
iterator
in interface java.util.Set
iterator
in class java.util.AbstractCollection
public java.util.Iterator descendingIterator()
descendingIterator
in interface NavigableSet
public boolean equals(java.lang.Object o)
equals
in interface java.util.Collection
equals
in interface java.util.Set
equals
in class java.util.AbstractSet
o
- the object to be compared for equality with this setpublic boolean removeAll(java.util.Collection c)
removeAll
in interface java.util.Collection
removeAll
in interface java.util.Set
removeAll
in class java.util.AbstractSet
c
- collection containing elements to be removed from this setjava.lang.ClassCastException
- if the types of one or more elements in this
set are incompatible with the specified collectionjava.lang.NullPointerException
- if the specified collection or any
of its elements are nullpublic java.lang.Object lower(java.lang.Object e)
NavigableSet
null
if there is no such element.lower
in interface NavigableSet
e
- the value to matche
,
or null
if there is no such elementjava.lang.ClassCastException
- if the specified element cannot be
compared with the elements currently in the setjava.lang.NullPointerException
- if the specified element is nullpublic java.lang.Object floor(java.lang.Object e)
NavigableSet
null
if there is no such element.floor
in interface NavigableSet
e
- the value to matche
,
or null
if there is no such elementjava.lang.ClassCastException
- if the specified element cannot be
compared with the elements currently in the setjava.lang.NullPointerException
- if the specified element is nullpublic java.lang.Object ceiling(java.lang.Object e)
NavigableSet
null
if there is no such element.ceiling
in interface NavigableSet
e
- the value to matche
,
or null
if there is no such elementjava.lang.ClassCastException
- if the specified element cannot be
compared with the elements currently in the setjava.lang.NullPointerException
- if the specified element is nullpublic java.lang.Object higher(java.lang.Object e)
NavigableSet
null
if there is no such element.higher
in interface NavigableSet
e
- the value to matche
,
or null
if there is no such elementjava.lang.ClassCastException
- if the specified element cannot be
compared with the elements currently in the setjava.lang.NullPointerException
- if the specified element is nullpublic java.lang.Object pollFirst()
NavigableSet
null
if this set is empty.pollFirst
in interface NavigableSet
null
if this set is emptypublic java.lang.Object pollLast()
NavigableSet
null
if this set is empty.pollLast
in interface NavigableSet
null
if this set is emptypublic java.util.Comparator comparator()
comparator
in interface java.util.SortedSet
public java.lang.Object first()
first
in interface java.util.SortedSet
NoSuchElementException
public java.lang.Object last()
last
in interface java.util.SortedSet
NoSuchElementException
public NavigableSet subSet(java.lang.Object fromElement, boolean fromInclusive, java.lang.Object toElement, boolean toInclusive)
NavigableSet
fromElement
to toElement
. If fromElement
and
toElement
are equal, the returned set is empty unless fromExclusive
and toExclusive
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
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
, exclusivejava.lang.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.java.lang.NullPointerException
- if fromElement
or
toElement
is nulljava.lang.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 headSet(java.lang.Object 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
toElement
- high endpoint of the returned setinclusive
- true
if the high endpoint
is to be included in the returned viewinclusive
is true) toElement
java.lang.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.java.lang.NullPointerException
- if toElement
is nulljava.lang.IllegalArgumentException
- if this set itself has a
restricted range, and toElement
lies outside the
bounds of the rangepublic NavigableSet tailSet(java.lang.Object 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
fromElement
- low endpoint of the returned setinclusive
- true
if the low endpoint
is to be included in the returned viewfromElement
java.lang.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.java.lang.NullPointerException
- if fromElement
is nulljava.lang.IllegalArgumentException
- if this set itself has a
restricted range, and fromElement
lies outside the
bounds of the rangepublic java.util.SortedSet subSet(java.lang.Object fromElement, java.lang.Object toElement)
NavigableSet
Equivalent to subSet(fromElement, true, toElement, false)
.
subSet
in interface NavigableSet
subSet
in interface java.util.SortedSet
java.lang.ClassCastException
java.lang.NullPointerException
- if fromElement
or
toElement
is nulljava.lang.IllegalArgumentException
public java.util.SortedSet headSet(java.lang.Object toElement)
NavigableSet
Equivalent to headSet(toElement, false)
.
headSet
in interface NavigableSet
headSet
in interface java.util.SortedSet
java.lang.ClassCastException
java.lang.NullPointerException
- if toElement
is nulljava.lang.IllegalArgumentException
public java.util.SortedSet tailSet(java.lang.Object fromElement)
NavigableSet
Equivalent to tailSet(fromElement, true)
.
tailSet
in interface NavigableSet
tailSet
in interface java.util.SortedSet
java.lang.ClassCastException
java.lang.NullPointerException
- if fromElement
is nulljava.lang.IllegalArgumentException
public NavigableSet 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