Interface NavigableSet<E>
- Type Parameters:
E
- the type of elements maintained by this set
- All Superinterfaces:
Collection<E>
,Iterable<E>
,SequencedCollection<E>
,SequencedSet<E>
,Set<E>
,SortedSet<E>
- All Known Implementing Classes:
ConcurrentSkipListSet
,TreeSet
SortedSet
extended with navigation methods reporting
closest matches for given search targets. Methods lower(E)
,
floor(E)
, ceiling(E)
, and higher(E)
return elements
respectively less than, less than or equal, greater than or equal,
and greater than a given element, returning null
if there
is no such element.
A NavigableSet
may be accessed and traversed in either
ascending or descending order. The descendingSet()
method
returns a view of the set with the senses of all relational and
directional methods inverted. The performance of ascending
operations and views is likely to be faster than that of descending
ones. This interface additionally defines methods pollFirst()
and pollLast()
that return and remove the lowest
and highest element, if one exists, else returning null
.
Methods
subSet(E, boolean, E, boolean)
,
headSet(E, boolean)
, and
tailSet(E, boolean)
differ from the like-named SortedSet
methods in accepting
additional arguments describing whether lower and upper bounds are
inclusive versus exclusive. Subsets of any NavigableSet
must implement the NavigableSet
interface.
The return values of navigation methods may be ambiguous in
implementations that permit null
elements. However, even
in this case the result can be disambiguated by checking
contains(null)
. To avoid such issues, implementations of
this interface are encouraged to not permit insertion of
null
elements. (Note that sorted sets of Comparable
elements intrinsically do not permit null
.)
Methods
subSet(E, E)
,
headSet(E)
, and
tailSet(E)
are specified to return SortedSet
to allow existing
implementations of SortedSet
to be compatibly retrofitted to
implement NavigableSet
, but extensions and implementations
of this interface are encouraged to override these methods to return
NavigableSet
.
This interface is a member of the Java Collections Framework.
- Since:
- 1.6
-
Method Summary
Modifier and TypeMethodDescriptionReturns the least element in this set greater than or equal to the given element, ornull
if there is no such element.Returns an iterator over the elements in this set, in descending order.Returns a reverse order view of the elements contained in this set.Returns the greatest element in this set less than or equal to the given element, ornull
if there is no such element.Returns a view of the portion of this set whose elements are strictly less thantoElement
.Returns a view of the portion of this set whose elements are less than (or equal to, ifinclusive
is true)toElement
.Returns the least element in this set strictly greater than the given element, ornull
if there is no such element.iterator()
Returns an iterator over the elements in this set, in ascending order.Returns the greatest element in this set strictly less than the given element, ornull
if there is no such element.Retrieves and removes the first (lowest) element, or returnsnull
if this set is empty (optional operation).pollLast()
Retrieves and removes the last (highest) element, or returnsnull
if this set is empty (optional operation).default E
Removes and returns the first element of this collection (optional operation).default E
Removes and returns the last element of this collection (optional operation).default NavigableSet
<E> reversed()
Returns a reverse-ordered view of this collection.Returns a view of the portion of this set whose elements range fromfromElement
totoElement
.Returns a view of the portion of this set whose elements range fromfromElement
, inclusive, totoElement
, exclusive.Returns a view of the portion of this set whose elements are greater than or equal tofromElement
.Returns a view of the portion of this set whose elements are greater than (or equal to, ifinclusive
is true)fromElement
.Methods inherited from interface java.util.Collection
parallelStream, removeIf, stream, toArray
Methods inherited from interface java.util.Set
add, addAll, clear, contains, containsAll, equals, hashCode, isEmpty, remove, removeAll, retainAll, size, toArray, toArray
Methods inherited from interface java.util.SortedSet
addFirst, addLast, comparator, first, getFirst, getLast, last, spliterator
-
Method Details
-
lower
Returns the greatest element in this set strictly less than the given element, ornull
if there is no such element.- Parameters:
e
- the value to match- Returns:
- the greatest element less than
e
, ornull
if there is no such element - Throws:
ClassCastException
- if the specified element cannot be compared with the elements currently in the setNullPointerException
- if the specified element is null and this set does not permit null elements
-
floor
Returns the greatest element in this set less than or equal to the given element, ornull
if there is no such element.- Parameters:
e
- the value to match- Returns:
- the greatest element less than or equal to
e
, ornull
if there is no such element - Throws:
ClassCastException
- if the specified element cannot be compared with the elements currently in the setNullPointerException
- if the specified element is null and this set does not permit null elements
-
ceiling
Returns the least element in this set greater than or equal to the given element, ornull
if there is no such element.- Parameters:
e
- the value to match- Returns:
- the least element greater than or equal to
e
, ornull
if there is no such element - Throws:
ClassCastException
- if the specified element cannot be compared with the elements currently in the setNullPointerException
- if the specified element is null and this set does not permit null elements
-
higher
Returns the least element in this set strictly greater than the given element, ornull
if there is no such element.- Parameters:
e
- the value to match- Returns:
- the least element greater than
e
, ornull
if there is no such element - Throws:
ClassCastException
- if the specified element cannot be compared with the elements currently in the setNullPointerException
- if the specified element is null and this set does not permit null elements
-
pollFirst
E pollFirst()Retrieves and removes the first (lowest) element, or returnsnull
if this set is empty (optional operation).- Returns:
- the first element, or
null
if this set is empty - Throws:
UnsupportedOperationException
- if thepollFirst
operation is not supported by this collection
-
pollLast
E pollLast()Retrieves and removes the last (highest) element, or returnsnull
if this set is empty (optional operation).- Returns:
- the last element, or
null
if this set is empty - Throws:
UnsupportedOperationException
- if thepollLast
operation is not supported by this collection
-
iterator
Returns an iterator over the elements in this set, in ascending order. -
descendingSet
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. If either set is modified while an iteration over either set is in progress (except through the iterator's ownremove
operation), the results of the iteration are undefined.The returned set has an ordering equivalent to
Collections.reverseOrder
(comparator())
. The expressions.descendingSet().descendingSet()
returns a view ofs
essentially equivalent tos
.- Returns:
- a reverse order view of this set
-
descendingIterator
-
subSet
Returns a view of the portion of this set whose elements range fromfromElement
totoElement
. IffromElement
andtoElement
are equal, the returned set is empty unlessfromInclusive
andtoInclusive
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
- 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 view- Returns:
- a view of the portion of this set whose elements range from
fromElement
, inclusive, totoElement
, exclusive - Throws:
ClassCastException
- iffromElement
andtoElement
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 iffromElement
ortoElement
cannot be compared to elements currently in the set.NullPointerException
- iffromElement
ortoElement
is null and this set does not permit null elementsIllegalArgumentException
- iffromElement
is greater thantoElement
; or if this set itself has a restricted range, andfromElement
ortoElement
lies outside the bounds of the range.
-
headSet
Returns a view of the portion of this set whose elements are less than (or equal to, ifinclusive
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
- high endpoint of the returned setinclusive
-true
if the high endpoint is to be included in the returned view- Returns:
- a view of the portion of this set whose elements are less than
(or equal to, if
inclusive
is true)toElement
- Throws:
ClassCastException
- iftoElement
is not compatible with this set's comparator (or, if the set has no comparator, iftoElement
does not implementComparable
). Implementations may, but are not required to, throw this exception iftoElement
cannot be compared to elements currently in the set.NullPointerException
- iftoElement
is null and this set does not permit null elementsIllegalArgumentException
- if this set itself has a restricted range, andtoElement
lies outside the bounds of the range
-
tailSet
Returns a view of the portion of this set whose elements are greater than (or equal to, ifinclusive
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
- low endpoint of the returned setinclusive
-true
if the low endpoint is to be included in the returned view- Returns:
- a view of the portion of this set whose elements are greater
than or equal to
fromElement
- Throws:
ClassCastException
- iffromElement
is not compatible with this set's comparator (or, if the set has no comparator, iffromElement
does not implementComparable
). Implementations may, but are not required to, throw this exception iffromElement
cannot be compared to elements currently in the set.NullPointerException
- iffromElement
is null and this set does not permit null elementsIllegalArgumentException
- if this set itself has a restricted range, andfromElement
lies outside the bounds of the range
-
subSet
Returns a view of the portion of this set whose elements range fromfromElement
, inclusive, totoElement
, exclusive. (IffromElement
andtoElement
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 interfaceSortedSet<E>
- Parameters:
fromElement
- low endpoint (inclusive) of the returned settoElement
- high endpoint (exclusive) of the returned set- Returns:
- a view of the portion of this set whose elements range from
fromElement
, inclusive, totoElement
, exclusive - Throws:
ClassCastException
- iffromElement
andtoElement
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 iffromElement
ortoElement
cannot be compared to elements currently in the set.NullPointerException
- iffromElement
ortoElement
is null and this set does not permit null elementsIllegalArgumentException
- iffromElement
is greater thantoElement
; or if this set itself has a restricted range, andfromElement
ortoElement
lies outside the bounds of the range
-
headSet
Returns a view of the portion of this set whose elements are strictly less thantoElement
. 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 interfaceSortedSet<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
- iftoElement
is not compatible with this set's comparator (or, if the set has no comparator, iftoElement
does not implementComparable
). Implementations may, but are not required to, throw this exception iftoElement
cannot be compared to elements currently in the set.NullPointerException
- iftoElement
is null and this set does not permit null elementsIllegalArgumentException
- if this set itself has a restricted range, andtoElement
lies outside the bounds of the range
-
tailSet
Returns a view of the portion of this set whose elements are greater than or equal tofromElement
. 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 interfaceSortedSet<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
- iffromElement
is not compatible with this set's comparator (or, if the set has no comparator, iffromElement
does not implementComparable
). Implementations may, but are not required to, throw this exception iffromElement
cannot be compared to elements currently in the set.NullPointerException
- iffromElement
is null and this set does not permit null elementsIllegalArgumentException
- if this set itself has a restricted range, andfromElement
lies outside the bounds of the range
-
removeFirst
Removes and returns the first element of this collection (optional operation).- Specified by:
removeFirst
in interfaceSequencedCollection<E>
- Specified by:
removeFirst
in interfaceSortedSet<E>
- Implementation Requirements:
- If this set is not empty, the implementation in this interface returns the result of calling
the
pollFirst
method. Otherwise, it throwsNoSuchElementException
. - Returns:
- the removed element
- Throws:
NoSuchElementException
- if this collection is emptyUnsupportedOperationException
- if this collection implementation does not support this operation- Since:
- 21
-
removeLast
Removes and returns the last element of this collection (optional operation).- Specified by:
removeLast
in interfaceSequencedCollection<E>
- Specified by:
removeLast
in interfaceSortedSet<E>
- Implementation Requirements:
- If this set is not empty, the implementation in this interface returns the result of calling
the
pollLast
method. Otherwise, it throwsNoSuchElementException
. - Returns:
- the removed element
- Throws:
NoSuchElementException
- if this collection is emptyUnsupportedOperationException
- if this collection implementation does not support this operation- Since:
- 21
-
reversed
Returns a reverse-ordered view of this collection. The encounter order of elements in the returned view is the inverse of the encounter order of elements in this collection. The reverse ordering affects all order-sensitive operations, including those on the view collections of the returned view. If the collection implementation permits modifications to this view, the modifications "write through" to the underlying collection. Changes to the underlying collection might or might not be visible in this reversed view, depending upon the implementation.This method is equivalent to
descendingSet
.- Specified by:
reversed
in interfaceSequencedCollection<E>
- Specified by:
reversed
in interfaceSequencedSet<E>
- Specified by:
reversed
in interfaceSortedSet<E>
- Implementation Requirements:
- The implementation in this interface returns the result of calling the
descendingSet
method. - Returns:
- a reverse-ordered view of this collection, as a
NavigableSet
- Since:
- 21
-