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>, SequencedMap<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.

The methods ceilingEntry(K), firstEntry(), floorEntry(K), higherEntry(K), lastEntry(), lowerEntry(K), pollFirstEntry(), and pollLastEntry() return Map.Entry instances that represent snapshots of mappings as of the time of the call. They do not support mutation of the underlying map via the optional setValue method.

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 Map

Map.Entry<K,V>

Modifier and Type	Interface	Description
`static interface`	`Map.Entry<K,V>`	A map entry (key-value pair).

Method Summary

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 (optional operation).
`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 (optional operation).
`default NavigableMap<K,V>`	`reversed()`	Returns a reverse-ordered view of this map.
`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 Map

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

Modifier and Type	Method	Description
`void`	`clear()`	Removes all of the mappings from this map (optional operation).
`default V`	`compute(K key, BiFunction<? super K, ? super V, ? extends V> remappingFunction)`	Attempts to compute a mapping for the specified key and its current mapped value, or `null` if there is no current mapping (optional operation).
`default V`	`computeIfAbsent(K key, Function<? super K, ? extends V> mappingFunction)`	If the specified key is not already associated with a value (or is mapped to `null`), attempts to compute its value using the given mapping function and enters it into this map unless `null` (optional operation).
`default V`	`computeIfPresent(K key, BiFunction<? super K, ? super V, ? extends V> remappingFunction)`	If the value for the specified key is present and non-null, attempts to compute a new mapping given the key and its current mapped value (optional operation).
`boolean`	`containsKey(Object key)`	Returns `true` if this map contains a mapping for the specified key.
`boolean`	`containsValue(Object value)`	Returns `true` if this map maps one or more keys to the specified value.
`boolean`	`equals(Object o)`	Compares the specified object with this map for equality.
`default void`	`forEach(BiConsumer<? super K, ? super V> action)`	Performs the given action for each entry in this map until all entries have been processed or the action throws an exception.
`V`	`get(Object key)`	Returns the value to which the specified key is mapped, or `null` if this map contains no mapping for the key.
`default V`	`getOrDefault(Object key, V defaultValue)`	Returns the value to which the specified key is mapped, or `defaultValue` if this map contains no mapping for the key.
`int`	`hashCode()`	Returns the hash code value for this map.
`boolean`	`isEmpty()`	Returns `true` if this map contains no key-value mappings.
`default V`	`merge(K key, V value, BiFunction<? super V, ? super V, ? extends V> remappingFunction)`	If the specified key is not already associated with a value or is associated with null, associates it with the given non-null value (optional operation).
`V`	`put(K key, V value)`	Associates the specified value with the specified key in this map (optional operation).
`void`	`putAll(Map<? extends K, ? extends V> m)`	Copies all of the mappings from the specified map to this map (optional operation).
`default V`	`putIfAbsent(K key, V value)`	If the specified key is not already associated with a value (or is mapped to `null`) associates it with the given value and returns `null`, else returns the current value (optional operation).
`V`	`remove(Object key)`	Removes the mapping for a key from this map if it is present (optional operation).
`default boolean`	`remove(Object key, Object value)`	Removes the entry for the specified key only if it is currently mapped to the specified value (optional operation).
`default V`	`replace(K key, V value)`	Replaces the entry for the specified key only if it is currently mapped to some value (optional operation).
`default boolean`	`replace(K key, V oldValue, V newValue)`	Replaces the entry for the specified key only if currently mapped to the specified value (optional operation).
`default void`	`replaceAll(BiFunction<? super K, ? super V, ? extends V> function)`	Replaces each entry's value with the result of invoking the given function on that entry until all entries have been processed or the function throws an exception (optional operation).
`int`	`size()`	Returns the number of key-value mappings in this map.

Methods declared in interface SequencedMap

sequencedEntrySet, sequencedKeySet, sequencedValues

Modifier and Type	Method	Description
`default SequencedSet<Map.Entry<K,V>>`	`sequencedEntrySet()`	Returns a `SequencedSet` view of this map's `entrySet`.
`default SequencedSet<K>`	`sequencedKeySet()`	Returns a `SequencedSet` view of this map's `keySet`.
`default SequencedCollection<V>`	`sequencedValues()`	Returns a `SequencedCollection` view of this map's `values` collection.

Methods declared in interface SortedMap

comparator, entrySet, firstKey, keySet, lastKey, putFirst, putLast, values

Modifier and Type	Method	Description
`Comparator<? super K>`	`comparator()`	Returns the comparator used to order the keys in this map, or `null` if this map uses the natural ordering of its keys.
`Set<Map.Entry<K,V>>`	`entrySet()`	Returns a `Set` view of the mappings contained in this map.
`K`	`firstKey()`	Returns the first (lowest) key currently in this map.
`Set<K>`	`keySet()`	Returns a `Set` view of the keys contained in this map.
`K`	`lastKey()`	Returns the last (highest) key currently in this map.
`default V`	`putFirst(K k, V v)`	Throws `UnsupportedOperationException`.
`default V`	`putLast(K k, V v)`	Throws `UnsupportedOperationException`.
`Collection<V>`	`values()`	Returns a `Collection` view of the values contained in this map.

Method Details

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.

Specified by:: firstEntry in interface SequencedMap<K,V>
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.

Specified by:: lastEntry in interface SequencedMap<K,V>
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 (optional operation).

Specified by:: pollFirstEntry in interface SequencedMap<K,V>
Returns:: the removed first entry of this map, or null if this map is empty
Throws:: UnsupportedOperationException - if the pollFirstEntry operation is not supported by this map

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 (optional operation).

Specified by:: pollLastEntry in interface SequencedMap<K,V>
Returns:: the removed last entry of this map, or null if this map is empty
Throws:: UnsupportedOperationException - if the pollLastEntry operation is not supported by this map

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

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.