Interface NavigableMap<K,V>

Type Parameters:: K - the type of keys maintained by this map; V - the type of mapped values

All Superinterfaces:: Map<K,V>, SortedMap<K,V>

All Known Subinterfaces:: ConcurrentNavigableMap<K,V>

All Known Implementing Classes:: ConcurrentSkipListMap, TreeMap

public interface NavigableMap<K,V>
extends SortedMap<K,V>

A SortedMap extended with navigation methods returning the closest matches for given search targets. Methods lowerEntry(K), floorEntry(K), ceilingEntry(K), and higherEntry(K) 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(K), floorKey(K), ceilingKey(K), and higherKey(K) 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(K, boolean, K, boolean), headMap(K, boolean), and tailMap(K, boolean) 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 overridden to return NavigableSet.

This interface is a member of the Java Collections Framework.

Since:: 1.6

Nested Class Summary

Nested classes/interfaces declared in interface java.util.Map

Map.Entry<K,V>

Method Summary

All Methods Instance Methods Abstract Methods
Modifier and Type	Method	Description
`Map.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.
`K`	`ceilingKey(K key)`	Returns the least key greater than or equal to the given key, or `null` if there is no such key.
`NavigableSet<K>`	`descendingKeySet()`	Returns a reverse order `NavigableSet` view of the keys contained in this map.
`NavigableMap<K,V>`	`descendingMap()`	Returns a reverse order view of the mappings contained in this map.
`Map.Entry<K,V>`	`firstEntry()`	Returns a key-value mapping associated with the least key in this map, or `null` if the map is empty.
`Map.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.
`K`	`floorKey(K key)`	Returns the greatest key less than or equal to the given key, or `null` if there is no such key.
`SortedMap<K,V>`	`headMap(K toKey)`	Returns a view of the portion of this map whose keys are strictly less than `toKey`.
`NavigableMap<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`.
`Map.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.
`K`	`higherKey(K key)`	Returns the least key strictly greater than the given key, or `null` if there is no such key.
`Map.Entry<K,V>`	`lastEntry()`	Returns a key-value mapping associated with the greatest key in this map, or `null` if the map is empty.
`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.
`K`	`lowerKey(K key)`	Returns the greatest key strictly less than the given key, or `null` if there is no such key.
`NavigableSet<K>`	`navigableKeySet()`	Returns a `NavigableSet` view of the keys contained in this map.
`Map.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.
`Map.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.
`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`.
`SortedMap<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.
`SortedMap<K,V>`	`tailMap(K fromKey)`	Returns a view of the portion of this map whose keys are greater than or equal to `fromKey`.
`NavigableMap<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`.

Methods declared in interface java.util.Map

clear, compute, computeIfAbsent, computeIfPresent, containsKey, containsValue, equals, forEach, get, getOrDefault, hashCode, isEmpty, merge, put, putAll, putIfAbsent, remove, remove, replace, replace, replaceAll, size

Methods declared in interface java.util.SortedMap

comparator, entrySet, firstKey, keySet, lastKey, values

Method Detail

lowerEntry

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.

Parameters:: key - the key
Returns:: an entry with the greatest key less than key, or null if there is no such key
Throws:: ClassCastException - if the specified key cannot be compared with the keys currently in the map; NullPointerException - if the specified key is null and this map does not permit null keys

lowerKey

K lowerKey(K key)

Returns the greatest key strictly less than the given key, or null if there is no such key.

Parameters:: key - the key
Returns:: the greatest key less than key, or null if there is no such key
Throws:: ClassCastException - if the specified key cannot be compared with the keys currently in the map; NullPointerException - if the specified key is null and this map does not permit null keys

floorEntry

Map.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.

Parameters:: key - the key
Returns:: an entry with the greatest key less than or equal to key, or null if there is no such key
Throws:: ClassCastException - if the specified key cannot be compared with the keys currently in the map; NullPointerException - if the specified key is null and this map does not permit null keys

floorKey

K floorKey(K key)

Returns the greatest key less than or equal to the given key, or null if there is no such key.

Parameters:: key - the key
Returns:: the greatest key less than or equal to key, or null if there is no such key
Throws:: ClassCastException - if the specified key cannot be compared with the keys currently in the map; NullPointerException - if the specified key is null and this map does not permit null keys

ceilingEntry

Map.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.

Parameters:: key - the key
Returns:: an entry with the least key greater than or equal to key, or null if there is no such key
Throws:: ClassCastException - if the specified key cannot be compared with the keys currently in the map; NullPointerException - if the specified key is null and this map does not permit null keys

ceilingKey

K ceilingKey(K key)

Returns the least key greater than or equal to the given key, or null if there is no such key.

Parameters:: key - the key
Returns:: the least key greater than or equal to key, or null if there is no such key
Throws:: ClassCastException - if the specified key cannot be compared with the keys currently in the map; NullPointerException - if the specified key is null and this map does not permit null keys

higherEntry

Map.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.

Parameters:: key - the key
Returns:: an entry with the least key greater than key, or null if there is no such key
Throws:: ClassCastException - if the specified key cannot be compared with the keys currently in the map; NullPointerException - if the specified key is null and this map does not permit null keys

higherKey

K higherKey(K key)

Returns the least key strictly greater than the given key, or null if there is no such key.

Parameters:: key - the key
Returns:: the least key greater than key, or null if there is no such key
Throws:: ClassCastException - if the specified key cannot be compared with the keys currently in the map; NullPointerException - if the specified key is null and this map does not permit null keys

firstEntry

Map.Entry<K,V> firstEntry()

Returns a key-value mapping associated with the least key in this map, or null if the map is empty.

Returns:: an entry with the least key, or null if this map is empty

lastEntry

Map.Entry<K,V> lastEntry()

Returns a key-value mapping associated with the greatest key in this map, or null if the map is empty.

Returns:: an entry with the greatest key, or null if this map is empty

pollFirstEntry

Map.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.

Returns:: the removed first entry of this map, or null if this map is empty

pollLastEntry

Map.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.

Returns:: the removed last entry of this map, or null if this map is empty

descendingMap

NavigableMap<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 Collections.reverseOrder(comparator()). The expression m.descendingMap().descendingMap() returns a view of m essentially equivalent to m.

Returns:: a reverse order view of this map

navigableKeySet

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.

Returns:: a navigable set view of the keys in this map

descendingKeySet

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.

Returns:: a reverse order navigable set view of the keys in this map

subMap

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.

Parameters:: fromKey - low endpoint of the keys in the returned map; fromInclusive - true if the low endpoint is to be included in the returned view; toKey - high endpoint of the keys in the returned map; toInclusive - true if the high endpoint is to be included in the returned view
Returns:: a view of the portion of this map whose keys range from fromKey to toKey
Throws:: 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 keys; IllegalArgumentException - 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 range

headMap

NavigableMap<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.