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NavigableMap

public interface NavigableMap
implements SortedMap<K, V>

java.util.NavigableMap<K, V>
Known Indirect Subclasses


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, keySet() can be overridden to return NavigableSet.

Summary

Public methods

abstract 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.

abstract K ceilingKey(K key)

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

abstract NavigableSet<K> descendingKeySet()

Returns a reverse order NavigableSet view of the keys contained in this map.

abstract NavigableMap<K, V> descendingMap()

Returns a reverse order view of the mappings contained in this map.

abstract Entry<K, V> firstEntry()

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

abstract 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.

abstract K floorKey(K key)

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

abstract SortedMap<K, V> headMap(K toKey)

Returns a view of the portion of this map whose keys are strictly less than toKey.

Equivalent to headMap(toKey, false).

abstract 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.

abstract 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.

abstract K higherKey(K key)

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

abstract Entry<K, V> lastEntry()

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

abstract 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.

abstract K lowerKey(K key)

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

abstract NavigableSet<K> navigableKeySet()

Returns a NavigableSet view of the keys contained in this map.

abstract 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.

abstract 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.

abstract 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.

Equivalent to subMap(fromKey, true, toKey, false).

abstract 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.

abstract 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.

abstract SortedMap<K, V> tailMap(K fromKey)

Returns a view of the portion of this map whose keys are greater than or equal to fromKey.

Equivalent to tailMap(fromKey, true).

Inherited methods

From interface java.util.SortedMap
From interface java.util.Map

Public methods

ceilingEntry

Added in API level 9
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 K: the key
Returns
Entry<K, V> 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

Added in API level 9
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 K: the key
Returns
K 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

descendingKeySet

Added in API level 9
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
NavigableSet<K> a reverse order navigable set view of the keys in this map

descendingMap

Added in API level 9
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
NavigableMap<K, V> a reverse order view of this map

firstEntry

Added in API level 9
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
Entry<K, V> an entry with the least key, or null if this map is empty

floorEntry

Added in API level 9
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 K: the key
Returns
Entry<K, V> 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

Added in API level 9
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 K: the key
Returns
K 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

headMap

Added in API level 11
SortedMap<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).

Parameters
toKey K: high endpoint (exclusive) of the keys in the returned map
Returns
SortedMap<K, V> a view of the portion of this map whose keys are strictly less than toKey
Throws
ClassCastException
NullPointerException
IllegalArgumentException

headMap

Added in API level 9
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.

The returned map will throw an IllegalArgumentException on an attempt to insert a key outside its range.

Parameters
toKey K: high endpoint of the keys in the returned map
inclusive boolean: true if the high endpoint is to be included in the returned view
Returns
NavigableMap<K, V> a view of the portion of this map whose keys are less than (or equal to, if inclusive is true) toKey
Throws
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 keys
IllegalArgumentException if this map itself has a restricted range, and toKey lies outside the bounds of the range

higherEntry

Added in API level 9
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 K: the key
Returns
Entry<K, V> 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

Added in API level 9
K higherKey (K key)

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

Parameters
key K: the key
Returns
K 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

lastEntry

Added in API level 9
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
Entry<K, V> an entry with the greatest key, or null if this map is empty

lowerEntry

Added in API level 9
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 K: the key
Returns
Entry<K, V> 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

Added in API level 9
K lowerKey (K key)

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

Parameters
key K: the key
Returns
K 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

navigableKeySet

Added in API level 9
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
NavigableSet<K> a navigable set view of the keys in this map

pollFirstEntry

Added in API level 9
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
Entry<K, V> the removed first entry of this map, or null if this map is empty

pollLastEntry

Added in API level 9
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
Entry<K, V> the removed last entry of this map, or null if this map is empty

subMap

Added in API level 11
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. (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).

Parameters
fromKey K: low endpoint (inclusive) of the keys in the returned map
toKey K: high endpoint (exclusive) of the keys in the returned map
Returns
SortedMap<K, V> a view of the portion of this map whose keys range from fromKey, inclusive, to toKey, exclusive
Throws
ClassCastException
NullPointerException
IllegalArgumentException

subMap

Added in API level 9
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 K: low endpoint of the keys in the returned map
fromInclusive boolean: true if the low endpoint is to be included in the returned view
toKey K: high endpoint of the keys in the returned map
toInclusive boolean: true if the high endpoint is to be included in the returned view
Returns
NavigableMap<K, V> 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

tailMap

Added in API level 9
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. 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.

Parameters
fromKey K: low endpoint of the keys in the returned map
inclusive boolean: true if the low endpoint is to be included in the returned view
Returns
NavigableMap<K, V> a view of the portion of this map whose keys are greater than (or equal to, if inclusive is true) fromKey
Throws
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 keys
IllegalArgumentException if this map itself has a restricted range, and fromKey lies outside the bounds of the range

tailMap

Added in API level 11
SortedMap<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).

Parameters
fromKey K: low endpoint (inclusive) of the keys in the returned map
Returns
SortedMap<K, V> a view of the portion of this map whose keys are greater than or equal to fromKey
Throws
ClassCastException
NullPointerException
IllegalArgumentException
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