E - the type of elements maintained by this setSerializable, Cloneable, Iterable<E>, Collection<E>, NavigableSet<E>, SequencedCollection<E>, SequencedSet<E>, Set<E>, SortedSet<E>
public 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 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.
Bulk operations that add, remove, or examine multiple elements, such as AbstractCollection.addAll(java.util.Collection<? extends E>), Collection.removeIf(java.util.function.Predicate<? super E>) or Iterable.forEach(java.util.function.Consumer<? super T>), are not guaranteed to be performed atomically. For example, a forEach traversal concurrent with an
addAll operation might observe 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 | Description |
|---|---|
ConcurrentSkipListSet() |
Constructs a new, empty set that orders its elements according to their natural ordering. |
ConcurrentSkipListSet |
Constructs a new set containing the elements in the specified collection, that orders its elements according to their natural ordering. |
ConcurrentSkipListSet |
Constructs a new, empty set that orders its elements according to the specified comparator. |
ConcurrentSkipListSet |
Constructs a new set containing the same elements and using the same ordering as the specified sorted set. |
| Modifier and Type | Method | Description |
|---|---|---|
boolean |
add |
Adds the specified element to this set if it is not already present. |
void |
addFirst |
Throws UnsupportedOperationException. |
void |
addLast |
Throws UnsupportedOperationException. |
E |
ceiling |
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 |
clone() |
Returns a shallow copy of this ConcurrentSkipListSet 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 |
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. |
boolean |
equals |
Compares the specified object with this set for equality. |
E |
first() |
Returns the first (lowest) element currently in this set. |
E |
floor |
Returns the greatest element in this set less than or equal to the given element, or null if there is no such element. |
NavigableSet |
headSet |
Returns a view of the portion of this set whose elements are strictly less than toElement. |
NavigableSet |
headSet |
Returns a view of the portion of this set whose elements are less than (or equal to, if inclusive is true) toElement. |
E |
higher |
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 |
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 |
Removes the specified element from this set if it is present. |
boolean |
removeAll |
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 |
spliterator() |
Returns a Spliterator over the elements in this set. |
NavigableSet |
subSet |
Returns a view of the portion of this set whose elements range from fromElement to toElement. |
NavigableSet |
subSet |
Returns a view of the portion of this set whose elements range from fromElement, inclusive, to toElement, exclusive. |
NavigableSet |
tailSet |
Returns a view of the portion of this set whose elements are greater than or equal to fromElement. |
NavigableSet |
tailSet |
Returns a view of the portion of this set whose elements are greater than (or equal to, if inclusive is true) fromElement. |
hashCode
addAll, containsAll, retainAll, toArray, toArray, toString
parallelStream, removeIf, stream, toArray
removeFirst, removeLast, reversed
public 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()
ConcurrentSkipListSet instance. (The elements themselves are not cloned.)public int size()
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.
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 elementspublic boolean contains(Object o)
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).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 element cannot be compared with the elements currently in this setNullPointerException - if the specified element is nullpublic boolean add(E e)
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.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 e cannot be compared with the elements currently in this setNullPointerException - if the specified element is nullpublic boolean remove(Object o)
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.)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 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 Collection<E>
iterator in interface Iterable<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)
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.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 settrue if the specified object is equal to this setpublic 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 settrue if this set changed as a result of the callClassCastException - 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 nullpublic 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()
SortedSetnull 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()
SortedSetfirst in interface SortedSet<E>
NoSuchElementException - if this set is emptypublic E last()
SortedSetlast in interface SortedSet<E>
NoSuchElementException - if this set is emptypublic void addFirst(E e)
UnsupportedOperationException. The encounter order induced by this set's comparison method determines the position of elements, so explicit positioning is not supported.addFirst in interface SequencedCollection<E>
addFirst in interface SortedSet<E>
e - the element to be addedUnsupportedOperationException - alwayspublic void addLast(E e)
UnsupportedOperationException. The encounter order induced by this set's comparison method determines the position of elements, so explicit positioning is not supported.addLast in interface SequencedCollection<E>
addLast in interface SortedSet<E>
e - the element to be added.UnsupportedOperationException - alwayspublic 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) 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 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 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 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)
NavigableSetfromElement, 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 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)
NavigableSettoElement. 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 nullIllegalArgumentException - if this set itself has a restricted range, and toElement lies outside the bounds of the rangepublic NavigableSet<E> tailSet(E fromElement)
NavigableSetfromElement. 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 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>
public Spliterator<E> spliterator()
Spliterator over the elements in this set. The Spliterator reports Spliterator.CONCURRENT, Spliterator.NONNULL, Spliterator.DISTINCT, Spliterator.SORTED and Spliterator.ORDERED, with an encounter order that is ascending order. Overriding implementations should document the reporting of additional characteristic values.
The spliterator's comparator is null if the set's comparator is null. Otherwise, the spliterator's comparator is the same as or imposes the same total ordering as the set's comparator.
spliterator in interface Collection<E>
spliterator in interface Iterable<E>
spliterator in interface Set<E>
spliterator in interface SortedSet<E>
Spliterator over the elements in this set
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https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/util/concurrent/ConcurrentSkipListSet.html