K
- the type of keys maintained by this mapV
- the type of mapped valuespublic interface NavigableMap<K,V> extends SortedMap<K,V>
A SortedMap
extended with navigation methods returning the closest matches for given search targets. Methods lowerEntry
, floorEntry
, ceilingEntry
, and higherEntry
return Map.Entry
objects associated with keys respectively less than, less than or equal, greater than or equal, and greater than a given key, returning null
if there is no such key. Similarly, methods lowerKey
, floorKey
, ceilingKey
, and higherKey
return only the associated keys. All of these methods are designed for locating, not traversing entries.
A NavigableMap
may be accessed and traversed in either ascending or descending key order. The descendingMap
method returns a view of the map 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. Methods subMap
, headMap
, and tailMap
differ from the like-named SortedMap
methods in accepting additional arguments describing whether lower and upper bounds are inclusive versus exclusive. Submaps of any NavigableMap
must implement the NavigableMap
interface.
This interface additionally defines methods firstEntry
, pollFirstEntry
, lastEntry
, and pollLastEntry
that return and/or remove the least and greatest mappings, if any exist, else returning null
.
Implementations of entry-returning methods are expected to return Map.Entry
pairs representing snapshots of mappings at the time they were produced, and thus generally do not support the optional Entry.setValue
method. Note however that it is possible to change mappings in the associated map using method put
.
Methods subMap(K, K)
, headMap(K)
, and tailMap(K)
are specified to return SortedMap
to allow existing implementations of SortedMap
to be compatibly retrofitted to implement NavigableMap
, but extensions and implementations of this interface are encouraged to override these methods to return NavigableMap
. Similarly, SortedMap.keySet()
can be overriden to return NavigableSet
.
This interface is a member of the Java Collections Framework.
Map.Entry<K,V>
Map.Entry<K,V> lowerEntry(K key)
Returns a key-value mapping associated with the greatest key strictly less than the given key, or null
if there is no such key.
key
- the keykey
, or null
if there is no such keyClassCastException
- if the specified key cannot be compared with the keys currently in the mapNullPointerException
- if the specified key is null and this map does not permit null keysK lowerKey(K key)
Returns the greatest key strictly less than the given key, or null
if there is no such key.
key
- the keykey
, or null
if there is no such keyClassCastException
- if the specified key cannot be compared with the keys currently in the mapNullPointerException
- if the specified key is null and this map does not permit null keysMap.Entry<K,V> floorEntry(K key)
Returns a key-value mapping associated with the greatest key less than or equal to the given key, or null
if there is no such key.
key
- the keykey
, or null
if there is no such keyClassCastException
- if the specified key cannot be compared with the keys currently in the mapNullPointerException
- if the specified key is null and this map does not permit null keysK floorKey(K key)
Returns the greatest key less than or equal to the given key, or null
if there is no such key.
key
- the keykey
, or null
if there is no such keyClassCastException
- if the specified key cannot be compared with the keys currently in the mapNullPointerException
- if the specified key is null and this map does not permit null keysMap.Entry<K,V> ceilingEntry(K key)
Returns a key-value mapping associated with the least key greater than or equal to the given key, or null
if there is no such key.
key
- the keykey
, or null
if there is no such keyClassCastException
- if the specified key cannot be compared with the keys currently in the mapNullPointerException
- if the specified key is null and this map does not permit null keysK ceilingKey(K key)
Returns the least key greater than or equal to the given key, or null
if there is no such key.
key
- the keykey
, or null
if there is no such keyClassCastException
- if the specified key cannot be compared with the keys currently in the mapNullPointerException
- if the specified key is null and this map does not permit null keysMap.Entry<K,V> higherEntry(K key)
Returns a key-value mapping associated with the least key strictly greater than the given key, or null
if there is no such key.
key
- the keykey
, or null
if there is no such keyClassCastException
- if the specified key cannot be compared with the keys currently in the mapNullPointerException
- if the specified key is null and this map does not permit null keysK higherKey(K key)
Returns the least key strictly greater than the given key, or null
if there is no such key.
key
- the keykey
, or null
if there is no such keyClassCastException
- if the specified key cannot be compared with the keys currently in the mapNullPointerException
- if the specified key is null and this map does not permit null keysMap.Entry<K,V> firstEntry()
Returns a key-value mapping associated with the least key in this map, or null
if the map is empty.
null
if this map is emptyMap.Entry<K,V> lastEntry()
Returns a key-value mapping associated with the greatest key in this map, or null
if the map is empty.
null
if this map is emptyMap.Entry<K,V> pollFirstEntry()
Removes and returns a key-value mapping associated with the least key in this map, or null
if the map is empty.
null
if this map is emptyMap.Entry<K,V> pollLastEntry()
Removes and returns a key-value mapping associated with the greatest key in this map, or null
if the map is empty.
null
if this map is emptyNavigableMap<K,V> descendingMap()
Returns a reverse order view of the mappings contained in this map. The descending map is backed by this map, so changes to the map are reflected in the descending map, and vice-versa. If either map is modified while an iteration over a collection view of either map is in progress (except through the iterator's own remove
operation), the results of the iteration are undefined.
The returned map has an ordering equivalent to
. The expression Collections.reverseOrder
(comparator())m.descendingMap().descendingMap()
returns a view of m
essentially equivalent to m
.
NavigableSet<K> navigableKeySet()
Returns a NavigableSet
view of the keys contained in this map. The set's iterator returns the keys in ascending order. The set is backed by the map, so changes to the map are reflected in the set, and vice-versa. If the map is modified while an iteration over the set is in progress (except through the iterator's own remove
operation), the results of the iteration are undefined. The set supports element removal, which removes the corresponding mapping from the map, via the Iterator.remove
, Set.remove
, removeAll
, retainAll
, and clear
operations. It does not support the add
or addAll
operations.
NavigableSet<K> descendingKeySet()
Returns a reverse order NavigableSet
view of the keys contained in this map. The set's iterator returns the keys in descending order. The set is backed by the map, so changes to the map are reflected in the set, and vice-versa. If the map is modified while an iteration over the set is in progress (except through the iterator's own remove
operation), the results of the iteration are undefined. The set supports element removal, which removes the corresponding mapping from the map, via the Iterator.remove
, Set.remove
, removeAll
, retainAll
, and clear
operations. It does not support the add
or addAll
operations.
NavigableMap<K,V> subMap(K fromKey, boolean fromInclusive, K toKey, boolean toInclusive)
Returns a view of the portion of this map whose keys range from fromKey
to toKey
. If fromKey
and toKey
are equal, the returned map is empty unless fromInclusive
and toInclusive
are both true. The returned map is backed by this map, so changes in the returned map are reflected in this map, and vice-versa. The returned map supports all optional map operations that this map supports.
The returned map will throw an IllegalArgumentException
on an attempt to insert a key outside of its range, or to construct a submap either of whose endpoints lie outside its range.
fromKey
- low endpoint of the keys in the returned mapfromInclusive
- true
if the low endpoint is to be included in the returned viewtoKey
- high endpoint of the keys in the returned maptoInclusive
- true
if the high endpoint is to be included in the returned viewfromKey
to toKey
ClassCastException
- if fromKey
and toKey
cannot be compared to one another using this map's comparator (or, if the map has no comparator, using natural ordering). Implementations may, but are not required to, throw this exception if fromKey
or toKey
cannot be compared to keys currently in the map.NullPointerException
- if fromKey
or toKey
is null and this map does not permit null keysIllegalArgumentException
- if fromKey
is greater than toKey
; or if this map itself has a restricted range, and fromKey
or toKey
lies outside the bounds of the rangeNavigableMap<K,V> headMap(K toKey, boolean inclusive)
Returns a view of the portion of this map whose keys are less than (or equal to, if inclusive
is true) toKey
. The returned map is backed by this map, so changes in the returned map are reflected in this map, and vice-versa. The returned map supports all optional map operations that this map supports.
The returned map will throw an IllegalArgumentException
on an attempt to insert a key outside its range.
toKey
- high endpoint of the keys in the returned mapinclusive
- true
if the high endpoint is to be included in the returned viewinclusive
is true) toKey
ClassCastException
- if toKey
is not compatible with this map's comparator (or, if the map has no comparator, if toKey
does not implement Comparable
). Implementations may, but are not required to, throw this exception if toKey
cannot be compared to keys currently in the map.NullPointerException
- if toKey
is null and this map does not permit null keysIllegalArgumentException
- if this map itself has a restricted range, and toKey
lies outside the bounds of the rangeNavigableMap<K,V> tailMap(K fromKey, boolean inclusive)
Returns a view of the portion of this map whose keys are greater than (or equal to, if inclusive
is true) fromKey
. The returned map is backed by this map, so changes in the returned map are reflected in this map, and vice-versa. The returned map supports all optional map operations that this map supports.
The returned map will throw an IllegalArgumentException
on an attempt to insert a key outside its range.
fromKey
- low endpoint of the keys in the returned mapinclusive
- true
if the low endpoint is to be included in the returned viewinclusive
is true) fromKey
ClassCastException
- if fromKey
is not compatible with this map's comparator (or, if the map has no comparator, if fromKey
does not implement Comparable
). Implementations may, but are not required to, throw this exception if fromKey
cannot be compared to keys currently in the map.NullPointerException
- if fromKey
is null and this map does not permit null keysIllegalArgumentException
- if this map itself has a restricted range, and fromKey
lies outside the bounds of the rangeSortedMap<K,V> subMap(K fromKey, K toKey)
Returns a view of the portion of this map whose keys range from fromKey
, inclusive, to toKey
, exclusive. (If fromKey
and toKey
are equal, the returned map is empty.) The returned map is backed by this map, so changes in the returned map are reflected in this map, and vice-versa. The returned map supports all optional map operations that this map supports.
The returned map will throw an IllegalArgumentException
on an attempt to insert a key outside its range.
Equivalent to subMap(fromKey, true, toKey, false)
.
subMap
in interface SortedMap<K,V>
fromKey
- low endpoint (inclusive) of the keys in the returned maptoKey
- high endpoint (exclusive) of the keys in the returned mapfromKey
, inclusive, to toKey
, exclusiveClassCastException
- if fromKey
and toKey
cannot be compared to one another using this map's comparator (or, if the map has no comparator, using natural ordering). Implementations may, but are not required to, throw this exception if fromKey
or toKey
cannot be compared to keys currently in the map.NullPointerException
- if fromKey
or toKey
is null and this map does not permit null keysIllegalArgumentException
- if fromKey
is greater than toKey
; or if this map itself has a restricted range, and fromKey
or toKey
lies outside the bounds of the rangeSortedMap<K,V> headMap(K toKey)
Returns a view of the portion of this map whose keys are strictly less than toKey
. The returned map is backed by this map, so changes in the returned map are reflected in this map, and vice-versa. The returned map supports all optional map operations that this map supports.
The returned map will throw an IllegalArgumentException
on an attempt to insert a key outside its range.
Equivalent to headMap(toKey, false)
.
headMap
in interface SortedMap<K,V>
toKey
- high endpoint (exclusive) of the keys in the returned maptoKey
ClassCastException
- if toKey
is not compatible with this map's comparator (or, if the map has no comparator, if toKey
does not implement Comparable
). Implementations may, but are not required to, throw this exception if toKey
cannot be compared to keys currently in the map.NullPointerException
- if toKey
is null and this map does not permit null keysIllegalArgumentException
- if this map itself has a restricted range, and toKey
lies outside the bounds of the rangeSortedMap<K,V> tailMap(K fromKey)
Returns a view of the portion of this map whose keys are greater than or equal to fromKey
. The returned map is backed by this map, so changes in the returned map are reflected in this map, and vice-versa. The returned map supports all optional map operations that this map supports.
The returned map will throw an IllegalArgumentException
on an attempt to insert a key outside its range.
Equivalent to tailMap(fromKey, true)
.
tailMap
in interface SortedMap<K,V>
fromKey
- low endpoint (inclusive) of the keys in the returned mapfromKey
ClassCastException
- if fromKey
is not compatible with this map's comparator (or, if the map has no comparator, if fromKey
does not implement Comparable
). Implementations may, but are not required to, throw this exception if fromKey
cannot be compared to keys currently in the map.NullPointerException
- if fromKey
is null and this map does not permit null keysIllegalArgumentException
- if this map itself has a restricted range, and fromKey
lies outside the bounds of the range
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