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- Type Parameters:
E
- the type of elements maintained by this set
- All Superinterfaces:
Collection<E>
,Iterable<E>
,Set<E>
,SortedSet<E>
- All Known Implementing Classes:
ConcurrentSkipListSet
,TreeSet
public interface NavigableSet<E> extends SortedSet<E>
ASortedSet
extended with navigation methods reporting closest matches for given search targets. Methodslower(E)
,floor(E)
,ceiling(E)
, andhigher(E)
return elements respectively less than, less than or equal, greater than or equal, and greater than a given element, returningnull
if there is no such element.A
NavigableSet
may be accessed and traversed in either ascending or descending order. ThedescendingSet()
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 methodspollFirst()
andpollLast()
that return and remove the lowest and highest element, if one exists, else returningnull
. MethodssubSet(E, boolean, E, boolean)
,headSet(E, boolean)
, andtailSet(E, boolean)
differ from the like-namedSortedSet
methods in accepting additional arguments describing whether lower and upper bounds are inclusive versus exclusive. Subsets of anyNavigableSet
must implement theNavigableSet
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 checkingcontains(null)
. To avoid such issues, implementations of this interface are encouraged to not permit insertion ofnull
elements. (Note that sorted sets ofComparable
elements intrinsically do not permitnull
.)Methods
subSet(E, E)
,headSet(E)
, andtailSet(E)
are specified to returnSortedSet
to allow existing implementations ofSortedSet
to be compatibly retrofitted to implementNavigableSet
, but extensions and implementations of this interface are encouraged to override these methods to returnNavigableSet
.This interface is a member of the Java Collections Framework.
- Since:
- 1.6
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Method Summary
All Methods Instance Methods Abstract Methods Modifier and Type Method Description E
ceiling(E e)
Returns the least element in this set greater than or equal to the given element, ornull
if there is no such 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.E
floor(E e)
Returns the greatest element in this set less than or equal to the given element, ornull
if there is no such element.SortedSet<E>
headSet(E toElement)
Returns a view of the portion of this set whose elements are strictly less thantoElement
.NavigableSet<E>
headSet(E toElement, boolean inclusive)
Returns a view of the portion of this set whose elements are less than (or equal to, ifinclusive
is true)toElement
.E
higher(E e)
Returns the least element in this set strictly greater than the given element, ornull
if there is no such element.Iterator<E>
iterator()
Returns an iterator over the elements in this set, in ascending order.E
lower(E e)
Returns the greatest element in this set strictly less than the given element, ornull
if there is no such element.E
pollFirst()
Retrieves and removes the first (lowest) element, or returnsnull
if this set is empty.E
pollLast()
Retrieves and removes the last (highest) element, or returnsnull
if this set is empty.NavigableSet<E>
subSet(E fromElement, boolean fromInclusive, E toElement, boolean toInclusive)
Returns a view of the portion of this set whose elements range fromfromElement
totoElement
.SortedSet<E>
subSet(E fromElement, E toElement)
Returns a view of the portion of this set whose elements range fromfromElement
, inclusive, totoElement
, exclusive.SortedSet<E>
tailSet(E fromElement)
Returns a view of the portion of this set whose elements are greater than or equal tofromElement
.NavigableSet<E>
tailSet(E fromElement, boolean inclusive)
Returns a view of the portion of this set whose elements are greater than (or equal to, ifinclusive
is true)fromElement
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Methods declared in interface java.util.Collection
parallelStream, removeIf, stream, toArray
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Methods declared in interface java.util.Set
add, addAll, clear, contains, containsAll, equals, hashCode, isEmpty, remove, removeAll, retainAll, size, toArray, toArray
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Methods declared in interface java.util.SortedSet
comparator, first, last, spliterator
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Method Detail
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lower
E lower(E e)
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
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floor
E floor(E e)
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
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ceiling
E ceiling(E e)
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
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higher
E higher(E e)
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
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pollFirst
E pollFirst()
Retrieves and removes the first (lowest) element, or returnsnull
if this set is empty.- Returns:
- the first element, or
null
if this set is empty
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pollLast
E pollLast()
Retrieves and removes the last (highest) element, or returnsnull
if this set is empty.- Returns:
- the last element, or
null
if this set is empty
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iterator
Iterator<E> iterator()
Returns an iterator over the elements in this set, in ascending order.
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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
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descendingIterator
Iterator<E> descendingIterator()
Returns an iterator over the elements in this set, in descending order. Equivalent in effect todescendingSet().iterator()
.- Returns:
- an iterator over the elements in this set, in descending order
-
subSet
NavigableSet<E> subSet(E fromElement, boolean fromInclusive, E toElement, boolean toInclusive)
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.
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headSet
NavigableSet<E> headSet(E toElement, boolean inclusive)
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
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tailSet
NavigableSet<E> tailSet(E fromElement, boolean inclusive)
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
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subSet
SortedSet<E> subSet(E fromElement, E toElement)
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
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headSet
SortedSet<E> headSet(E toElement)
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
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tailSet
SortedSet<E> tailSet(E fromElement)
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
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