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java.util.concurrent
Class ConcurrentSkipListSet<E>
java.lang.Object
java.util.AbstractCollection<E>
java.util.AbstractSet<E>
java.util.concurrent.ConcurrentSkipListSet<E>
-
-
Type Parameters:
-
E - the type of elements maintained by this set
-
All Implemented Interfaces:
-
Serializable
,
Cloneable
,
Iterable
<E>,
Collection
<E>,
NavigableSet
<E>,
Set
<E>,
SortedSet
<E>
-
public class ConcurrentSkipListSet<E>
- extends AbstractSet<E>
- implements NavigableSet<E>, Cloneable, Serializable
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 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
Java Collections Framework
.
-
Since:
-
1.6
-
See Also:
-
Serialized Form
Method Summary
|
boolean |
add
(
E
e)
Adds the specified element to this set if it is not already present. |
E
|
ceiling
(
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
Returns the greatest element in this set less than or equal to the given element, or
null
if there is no such element. |
NavigableSet
SortedSet
<
E
|
headSet
(
E
Returns a view of the portion of this set whose elements are strictly less than
Equivalent to
navigableHeadSet(E)
toElement
SortedSet
.
interface.
|
NavigableSet
<
E
|
headSet
higher
(
E
Returns
a view of
the
portion of
least element in
this set
whose elements are less
strictly greater
than
(or equal to,
the given element, or
null
if
inclusive
there
is
true) toElement.
no such element.
|
E
|
higher
(
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
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.
|
NavigableSet
<
E
|
navigableHeadSet
(
E
Returns a view of the portion of this set whose elements are strictly less than
toElement
.
|
E
|
pollLast
()
Retrieves and removes the last (highest) element, or returns null if this set is empty.
|
NavigableSet
<
E
|
navigableSubSet
(
E
fromElement,
E
Returns a view of the portion of this set whose elements range from
fromElement
, inclusive, to
toElement
, exclusive.
|
NavigableSet
<
E
|
navigableTailSet
(
E
Returns a view of the portion of this set whose elements are greater than or equal to
fromElement
.
|
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
SortedSet
<
E
|
subSet
subSet
(
E
fromElement,
boolean fromInclusive,
E
Returns a view of the portion of this set whose elements range from fromElement
Equivalent
to
toElement.
navigableSubSet(E, E)
SortedSet
interface.
|
NavigableSet
SortedSet
<
E
|
subSet
tailSet
(
E
fromElement,
E
Returns a view of the portion of this set whose elements range from
fromElement
, inclusive,
Equivalent
to
navigableTailSet(E)
toElement
SortedSet
, exclusive.
interface.
|
NavigableSet
<
E
|
tailSet
(
E
Returns a view of the portion of this set whose elements are greater than or equal to
fromElement
.
|
NavigableSet
<
E
|
tailSet
(
E
Returns a view of the portion of this set whose elements are greater than (or equal to, if inclusive is true) fromElement.
|
ConcurrentSkipListSet
public ConcurrentSkipListSet()
-
Constructs a new, empty set that orders its elements according to their
natural ordering
.
ConcurrentSkipListSet
public ConcurrentSkipListSet(Comparator<? super E> comparator)
-
Constructs a new, empty set that orders its elements according to the specified comparator.
-
Parameters:
-
comparator - the comparator that will be used to order this set. If
null
, the
natural ordering
of the elements will be used.
ConcurrentSkipListSet
public 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 - 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
public ConcurrentSkipListSet(SortedSet<E> s)
-
Constructs a new set containing the same elements and using the same ordering as the specified sorted set.
-
Parameters:
-
s - sorted set whose elements will comprise the new set
-
Throws:
-
NullPointerException
- if the specified sorted set or any of its elements are null
clone
public ConcurrentSkipListSet<E> clone()
-
Returns a shallow copy of this
ConcurrentSkipListSet
instance. (The elements themselves are not cloned.)
-
-
Overrides:
-
clone
in class
Object
-
-
Returns:
-
a shallow copy of this set
-
See Also:
-
Cloneable
size
public 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.
-
-
Specified by:
-
size
in interface
Collection
<
E
>
-
Specified by:
-
size
in interface
Set
<
E
>
-
Specified by:
-
size
in class
AbstractCollection
<
E
>
-
-
Returns:
-
the number of elements in this set
isEmpty
public boolean isEmpty()
-
Returns
true
if this set contains no elements.
-
-
Specified by:
-
isEmpty
in interface
Collection
<
E
>
-
Specified by:
-
isEmpty
in interface
Set
<
E
>
-
Overrides:
-
isEmpty
in class
AbstractCollection
<
E
>
-
-
Returns:
-
true
if this set contains no elements
contains
public 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)
.
-
-
Specified by:
-
contains
in interface
Collection
<
E
>
-
Specified by:
-
contains
in interface
Set
<
E
>
-
Overrides:
-
contains
in class
AbstractCollection
<
E
>
-
-
Parameters:
-
o - object to be checked for containment in this set
-
Returns:
-
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
add
public 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
.
-
-
Specified by:
-
add
in interface
Collection
<
E
>
-
Specified by:
-
add
in interface
Set
<
E
>
-
Overrides:
-
add
in class
AbstractCollection
<
E
>
-
-
Parameters:
-
e - element to be added to this set
-
Returns:
-
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
remove
public 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.)
-
-
Specified by:
-
remove
in interface
Collection
<
E
>
-
Specified by:
-
remove
in interface
Set
<
E
>
-
Overrides:
-
remove
in class
AbstractCollection
<
E
>
-
-
Parameters:
-
o - object to be removed from this set, if present
-
Returns:
-
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
clear
public void clear()
-
Removes all of the elements from this set.
-
-
Specified by:
-
clear
in interface
Collection
<
E
>
-
Specified by:
-
clear
in interface
Set
<
E
>
-
Overrides:
-
clear
in class
AbstractCollection
<
E
>
-
iterator
public Iterator<E> iterator()
-
Returns an iterator over the elements in this set in ascending order.
-
-
Specified by:
-
iterator
in interface
Iterable
<
E
>
-
Specified by:
-
iterator
in interface
Collection
<
E
>
-
Specified by:
-
iterator
in interface
NavigableSet
<
E
>
-
Specified by:
-
iterator
in interface
Set
<
E
>
-
Specified by:
-
iterator
in class
AbstractCollection
<
E
>
-
-
Returns:
-
an iterator over the elements in this set in ascending order
descendingIterator
public Iterator<E> descendingIterator()
-
Returns an iterator over the elements in this set in descending order.
-
-
Specified by:
-
descendingIterator
in interface
NavigableSet
<
E
>
-
-
Returns:
-
an iterator over the elements in this set in descending order
equals
public 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.
-
-
Specified by:
-
equals
in interface
Collection
<
E
>
-
Specified by:
-
equals
in interface
Set
<
E
>
-
Overrides:
-
equals
in class
AbstractSet
<
E
>
-
-
Parameters:
-
o - the object to be compared for equality with this set
-
Returns:
-
true
if the specified object is equal to this set
-
See Also:
-
Object.hashCode()
,
Hashtable
removeAll
public 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.
-
-
Specified by:
-
removeAll
in interface
Collection
<
E
>
-
Specified by:
-
removeAll
in interface
Set
<
E
>
-
Overrides:
-
removeAll
in class
AbstractSet
<
E
>
-
-
Parameters:
-
c - collection containing elements to be removed from this set
-
Returns:
-
true
if this set changed as a result of the call
-
Throws:
-
ClassCastException
- if the types of one or more elements in this set are incompatible with the specified collection
-
NullPointerException
- if the specified collection or any of its elements are null
-
See Also:
-
AbstractCollection.remove(Object)
,
AbstractCollection.contains(Object)
lower
public 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.
-
-
Specified by:
-
lower
in interface
NavigableSet
<
E
>
-
-
Parameters:
-
e - the value to match
-
Returns:
-
the greatest element less than
e,
e
,
or
null
if there is no such element -
Throws:
-
ClassCastException
- if the specified element cannot be compared with the elements currently in the set
-
NullPointerException
- if the specified element is null
floor
public 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.
-
-
Specified by:
-
floor
in interface
NavigableSet
<
E
>
-
-
Parameters:
-
e - the value to match
-
Returns:
-
the greatest element less than or equal to
e,
e
,
or
null
if there is no such element -
Throws:
-
ClassCastException
- if the specified element cannot be compared with the elements currently in the set
-
NullPointerException
- if the specified element is null
ceiling
public 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.
-
-
Specified by:
-
ceiling
in interface
NavigableSet
<
E
>
-
-
Parameters:
-
e - the value to match
-
Returns:
-
the least element greater than or equal to
e,
e
,
or
null
if there is no such element -
Throws:
-
ClassCastException
- if the specified element cannot be compared with the elements currently in the set
-
NullPointerException
- if the specified element is null
higher
public 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.
-
-
Specified by:
-
higher
in interface
NavigableSet
<
E
>
-
-
Parameters:
-
e - the value to match
-
Returns:
-
the least element greater than
e,
e
,
or
null
if there is no such element -
Throws:
-
ClassCastException
- if the specified element cannot be compared with the elements currently in the set
-
NullPointerException
- if the specified element is null
pollFirst
public E pollFirst()
-
Description copied from interface:
NavigableSet
-
Retrieves and removes the first (lowest) element, or returns
null
if this set is empty.
-
-
Specified by:
-
pollFirst
in interface
NavigableSet
<
E
>
-
-
Returns:
-
the first element, or
null
if this set is empty
pollLast
public E pollLast()
-
Description copied from interface:
NavigableSet
-
Retrieves and removes the last (highest) element, or returns
null
if this set is empty.
-
-
Specified by:
-
pollLast
in interface
NavigableSet
<
E
>
-
-
Returns:
-
the last element, or
null
if this set is empty
comparator
public 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.
-
-
Specified by:
-
comparator
in interface
SortedSet
<
E
>
-
-
Returns:
-
the comparator used to order the elements in this set, or
null
if this set uses the natural ordering of its elements
first
public E first()
-
Description copied from interface:
SortedSet
-
Returns the first (lowest) element currently in this set.
-
-
Specified by:
-
first
in interface
SortedSet
<
E
>
-
-
Returns:
-
the first (lowest) element currently in this set
-
Throws:
-
NoSuchElementException
- if this set is empty
last
public E last()
-
Description copied from interface:
SortedSet
-
Returns the last (highest) element currently in this set.
-
-
Specified by:
-
last
in interface
SortedSet
<
E
>
-
-
Returns:
-
the last (highest) element currently in this set
-
Throws:
-
NoSuchElementException
- if this set is empty
subSet
navigableSubSet
public NavigableSet<E> subSet navigableSubSet (E fromElement,
boolean fromInclusive,
E toElement,
boolean toInclusive) toElement)
-
Description copied from interface:
NavigableSet
NavigableSet
-
Returns a view of the portion of this set whose elements range from
fromElement
, inclusive,
to
toElement. If
toElement
, exclusive. (If
fromElement
and
toElement
are equal, the returned set is
empty unless fromExclusive and toExclusive are both true.
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.
-
-
Specified by:
-
subSet
navigableSubSet
in interface
NavigableSet
<
E
>
-
-
Parameters:
-
fromElement - low endpoint
(inclusive)
of the returned set -
fromInclusive - true if the low endpoint is to be included in the returned view
-
toElement - high endpoint of the returned set
-
toInclusive - true if the high endpoint is to be included in the returned view
toElement - high endpoint (exclusive) of the returned set
-
Returns:
-
a view of the portion of this set whose elements range from
fromElement,
fromElement
,
inclusive, to
toElement,
toElement
,
exclusive -
Throws:
-
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.
-
NullPointerException
- if
fromElement
or
toElement
is null
-
IllegalArgumentException
- if
fromElement
is greater than
toElement;
toElement
;
or if this set itself has a restricted range, and
fromElement
or
toElement
lies outside the bounds of the range.
headSet
navigableHeadSet
public NavigableSet<E> headSet navigableHeadSet (E toElement,
boolean inclusive) toElement)
-
Description copied from interface:
NavigableSet
NavigableSet
-
Returns a view of the portion of this set whose elements are
strictly
less than
(or equal to, if inclusive is true) toElement.
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.
-
-
Specified by:
-
headSet
navigableHeadSet
in interface
NavigableSet
<
E
>
-
-
Parameters:
-
toElement - high endpoint of the returned set
-
inclusive - true if the high endpoint is to be included in the returned view
toElement - high endpoint (exclusive) of the returned set
-
Returns:
-
a view of the portion of this set whose elements are
strictly
less than
(or equal to, if inclusive is true)
toElement
-
Throws:
-
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
-
IllegalArgumentException
- if this set itself has a restricted range, and
toElement
lies outside the bounds of the range
tailSet
navigableTailSet
public NavigableSet<E> tailSet navigableTailSet (E fromElement,
boolean inclusive) fromElement)
-
Description copied from interface:
NavigableSet
NavigableSet
-
Returns a view of the portion of this set whose elements are greater than
(or
or
equal
to, if inclusive is true) fromElement.
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.
-
-
Specified by:
-
tailSet
navigableTailSet
in interface
NavigableSet
<
E
>
-
-
Parameters:
-
fromElement - low endpoint of the returned set
-
inclusive - true if the low endpoint is to be included in the returned view
fromElement - low endpoint (inclusive) of the returned set
-
Returns:
-
a view of the portion of this set whose elements are greater than or equal to
fromElement
-
Throws:
-
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
-
IllegalArgumentException
- if this set itself has a restricted range, and
fromElement
lies outside the bounds of the range
subSet
public NavigableSetSortedSet<E> subSet(E fromElement,
E toElement)
-
Description copied from interface:
NavigableSet
Equivalent to
navigableSubSet(E, E)
-
but with a return type conforming to the
SortedSet
interface.
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).
-
-
Specified by:
-
subSet
in interface
NavigableSet
<
E
>
-
Specified by:
-
subSet
in interface
SortedSet
<
E
>
-
-
Parameters:
-
fromElement - low endpoint (inclusive) of the returned set
-
toElement - high endpoint (exclusive) of the returned set
-
Returns:
-
a view of the portion of this set whose elements range from
fromElement
, inclusive, to
toElement
, exclusive
-
Throws:
-
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.
-
NullPointerException
- if
fromElement
or
toElement
is null
-
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
headSet
public NavigableSetSortedSet<E> headSet(E toElement)
-
Description copied from interface:
NavigableSet
Equivalent to
navigableHeadSet(E)
-
but with a return type conforming to the
SortedSet
interface.
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).
-
-
Specified by:
-
headSet
in interface
NavigableSet
<
E
>
-
Specified by:
-
headSet
in interface
SortedSet
<
E
>
-
-
Parameters:
-
toElement - high endpoint (exclusive) of the returned set
-
Returns:
-
a view of the portion of this set whose elements are strictly less than
toElement
-
Throws:
-
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
-
IllegalArgumentException
- if this set itself has a restricted range, and
toElement
lies outside the bounds of the
rangena
range
tailSet
public NavigableSetSortedSet<E> tailSet(E fromElement)
-
Description copied from interface:
NavigableSet
Equivalent to
navigableTailSet(E)
-
but with a return type conforming to the
SortedSet
interface.
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).
-
-
Specified by:
-
tailSet
in interface
NavigableSet
<
E
>
-
Specified by:
-
tailSet
in interface
SortedSet
<
E
>
-
-
Parameters:
-
fromElement - low endpoint (inclusive) of the returned set
-
Returns:
-
a view of the portion of this set whose elements are greater than or equal to
fromElement
-
Throws:
-
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
-
IllegalArgumentException
- if this set itself has a restricted range, and
fromElement
lies outside the bounds of the range
descendingSet
public 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.
-
-
Specified by:
-
descendingSet
in interface
NavigableSet
<
E
>
-
-
Returns:
-
a reverse order view of this set