E
- the type of elements maintained by this set
public interface NavigableSet<E> extends SortedSet<E>
SortedSet
extended with navigation methods reporting closest matches for given search targets. Methods
lower
,
floor
,
ceiling
, and
higher
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
,
headSet
, and
tailSet
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.
Modifier and Type | Method and Description |
---|---|
E |
ceiling(E e)
Returns the least element in this set greater than or equal to the given element, or
null if there is no such 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.
|
E |
floor(E e)
Returns the greatest element in this set less than or equal to the given element, or
null if there is no such element.
|
SortedSet |
headSet(E toElement)
Returns a view of the portion of this set whose elements are strictly less than
toElement.
|
NavigableSet |
headSet(E 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 .
|
E |
higher(E e)
Returns the least element in this set strictly greater than the given element, or
null if there is no such element.
|
Iterator |
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, 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.
|
NavigableSet |
subSet(E fromElement, boolean fromInclusive, E toElement, boolean toInclusive)
Returns a view of the portion of this set whose elements range from
fromElement to
toElement .
|
SortedSet |
subSet(E fromElement, E toElement)
Returns a view of the portion of this set whose elements range from
fromElement, inclusive, to
toElement, exclusive.
|
SortedSet |
tailSet(E fromElement)
Returns a view of the portion of this set whose elements are greater than or equal to
fromElement.
|
NavigableSet |
tailSet(E 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 .
|
comparator, first, last, spliterator
add, addAll, clear, contains, containsAll, equals, hashCode, isEmpty, remove, removeAll, retainAll, size, toArray, toArray
parallelStream, removeIf, stream
E lower(E e)
null
if there is no such element.
e
- the value to match
e
, or
null
if there is no such element
ClassCastException
- if the specified element cannot be compared with the elements currently in the set
NullPointerException
- if the specified element is null and this set does not permit null elements
E floor(E e)
null
if there is no such element.
e
- the value to match
e
, or
null
if there is no such element
ClassCastException
- if the specified element cannot be compared with the elements currently in the set
NullPointerException
- if the specified element is null and this set does not permit null elements
E ceiling(E e)
null
if there is no such element.
e
- the value to match
e
, or
null
if there is no such element
ClassCastException
- if the specified element cannot be compared with the elements currently in the set
NullPointerException
- if the specified element is null and this set does not permit null elements
E higher(E e)
null
if there is no such element.
e
- the value to match
e
, or
null
if there is no such element
ClassCastException
- if the specified element cannot be compared with the elements currently in the set
NullPointerException
- if the specified element is null and this set does not permit null elements
E pollFirst()
null
if this set is empty.
null
if this set is empty
E pollLast()
null
if this set is empty.
null
if this set is empty
Iterator<E> iterator()
NavigableSet<E> descendingSet()
remove
operation), the results of the iteration are undefined.
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
.
Iterator<E> descendingIterator()
descendingSet().iterator()
.
NavigableSet<E> subSet(E fromElement, boolean fromInclusive, E toElement, boolean toInclusive)
fromElement
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.
fromElement
- low endpoint 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
fromElement
, inclusive, to
toElement
, exclusive
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 and this set does not permit null elements
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.
NavigableSet<E> headSet(E toElement, boolean inclusive)
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.
toElement
- high endpoint of the returned set
inclusive
-
true
if the high endpoint is to be included in the returned view
inclusive
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 null and this set does not permit null elements
IllegalArgumentException
- if this set itself has a restricted range, and
toElement
lies outside the bounds of the range
NavigableSet<E> tailSet(E fromElement, boolean inclusive)
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.
fromElement
- low endpoint of the returned set
inclusive
-
true
if the low endpoint is to be included in the returned view
fromElement
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 and this set does not permit null elements
IllegalArgumentException
- if this set itself has a restricted range, and
fromElement
lies outside the bounds of the range
SortedSet<E> subSet(E fromElement, E toElement)
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
SortedSet<E>
fromElement
- low endpoint (inclusive) of the returned set
toElement
- high endpoint (exclusive) of the returned set
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 and this set does not permit null elements
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
SortedSet<E> headSet(E toElement)
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
SortedSet<E>
toElement
- high endpoint (exclusive) of the returned set
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 and this set does not permit null elements
IllegalArgumentException
- if this set itself has a restricted range, and
toElement lies outside the bounds of the range
SortedSet<E> tailSet(E fromElement)
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
SortedSet<E>
fromElement
- low endpoint (inclusive) of the returned set
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 and this set does not permit null elements
IllegalArgumentException
- if this set itself has a restricted range, and
fromElement lies outside the bounds of the range