Interface NavigableSet<E>
- 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>
A 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 Type | Method | Description |
---|---|---|
E | ceiling(E e) | Returns the least element in this set greater than or equal to the given element, or |
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, or |
SortedSet<E> | headSet(E toElement) | Returns a view of the portion of this set whose elements are strictly less than |
NavigableSet<E> | headSet(E toElement,
boolean inclusive) | Returns a view of the portion of this set whose elements are less than (or equal to, if |
E | higher(E e) | Returns the least element in this set strictly greater than the given element, or |
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, or |
E | pollFirst() | Retrieves and removes the first (lowest) element, or returns |
E | pollLast() | Retrieves and removes the last (highest) element, or returns |
NavigableSet<E> | subSet(E fromElement,
boolean fromInclusive,
E toElement,
boolean toInclusive) | Returns a view of the portion of this set whose elements range from |
SortedSet<E> | subSet(E fromElement,
E toElement) | Returns a view of the portion of this set whose elements range from |
SortedSet<E> | tailSet(E fromElement) | Returns a view of the portion of this set whose elements are greater than or equal to |
NavigableSet<E> | tailSet(E fromElement,
boolean inclusive) | Returns a view of the portion of this set whose elements are greater than (or equal to, if |
Methods declared in interface java.util.Collection
parallelStream, removeIf, stream, toArray
Methods declared in interface java.lang.Iterable
forEach
Methods declared in interface java.util.Set
add, addAll, clear, contains, containsAll, equals, hashCode, isEmpty, remove, removeAll, retainAll, size, toArray, toArray
Methods declared in interface java.util.SortedSet
comparator, first, last, spliterator
Method Detail
lower
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.
- 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 set -
NullPointerException
- if the specified element is null and this set does not permit null elements
floor
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.
- 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 set -
NullPointerException
- if the specified element is null and this set does not permit null elements
ceiling
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.
- 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 set -
NullPointerException
- if the specified element is null and this set does not permit null elements
higher
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.
- 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 set -
NullPointerException
- 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 returns null
if this set is empty.
- Returns:
- the first element, or
null
if this set is empty
pollLast
E pollLast()
Retrieves and removes the last (highest) element, or returns null
if this set is empty.
- Returns:
- the last element, or
null
if this set is empty
iterator
Iterator<E> iterator()
Returns an iterator over the elements in this set, in ascending order.
- Specified by:
-
iterator
in interfaceCollection<E>
- Specified by:
-
iterator
in interfaceIterable<E>
- Specified by:
-
iterator
in interfaceSet<E>
- 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 own 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
.
- Returns:
- a reverse order view of this set
descendingIterator
Iterator<E> descendingIterator()
Returns an iterator over the elements in this set, in descending order. Equivalent in effect to descendingSet().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 from 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.
- Parameters:
-
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 - 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 elements -
IllegalArgumentException
- iffromElement
is greater thantoElement
; or if this set itself has a restricted range, andfromElement
ortoElement
lies outside the bounds of the range.
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, if 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.
- Parameters:
-
toElement
- high endpoint of the returned set -
inclusive
-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 elements -
IllegalArgumentException
- if this set itself has a restricted range, andtoElement
lies outside the bounds of the range
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, if 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.
- Parameters:
-
fromElement
- low endpoint of the returned set -
inclusive
-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 elements -
IllegalArgumentException
- if this set itself has a restricted range, andfromElement
lies outside the bounds of the range
subSet
SortedSet<E> subSet(E fromElement, E toElement)
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 interfaceSortedSet<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, 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 elements -
IllegalArgumentException
- iffromElement
is greater thantoElement
; or if this set itself has a restricted range, andfromElement
ortoElement
lies outside the bounds of the range
headSet
SortedSet<E> headSet(E toElement)
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 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 elements -
IllegalArgumentException
- if this set itself has a restricted range, andtoElement
lies outside the bounds of the range
tailSet
SortedSet<E> tailSet(E fromElement)
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 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 elements -
IllegalArgumentException
- if this set itself has a restricted range, andfromElement
lies outside the bounds of the range