java.util

Interface NavigableMap<K,V>

All Superinterfaces:
Map<K,V>, SortedMap<K,V>
Known Subinterfaces:
ConcurrentNavigableMap<K,V>
Known Implementing Classes:
ConcurrentSkipListMap<K,V>, TreeMap<K,V>

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, 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, keySet() can be overriden to return NavigableSet.

This interface is a member of the ../../../technotes/guides/collections/index.html"> Java Collections Framework.

Since:
1.6

Method Summary

java.util.Map.Entry
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
descendingKeySet()
Returns a reverse order NavigableSet view of the keys contained in this map.
NavigableMap
descendingMap()
Returns a reverse order view of the mappings contained in this map.
java.util.Map.Entry
firstEntry()
Returns a key-value mapping associated with the least key in this map, or null if the map is empty.
java.util.Map.Entry
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
headMap(K toKey)
Equivalent to headMap(toKey, false).
NavigableMap
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.
java.util.Map.Entry
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.
java.util.Map.Entry
lastEntry()
Returns a key-value mapping associated with the greatest key in this map, or null if the map is empty.
java.util.Map.Entry
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
navigableKeySet()
Returns a NavigableSet view of the keys contained in this map.
java.util.Map.Entry
pollFirstEntry()
Removes and returns a key-value mapping associated with the least key in this map, or null if the map is empty.
java.util.Map.Entry
pollLastEntry()
Removes and returns a key-value mapping associated with the greatest key in this map, or null if the map is empty.
SortedMap
subMap(K fromKey, K toKey)
Equivalent to subMap(fromKey, true, toKey, false).
NavigableMap
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
tailMap(K fromKey)
Equivalent to tailMap(fromKey, true).
NavigableMap
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 inherited from interface java.util.Map<K,V>

V>> entrySet, clear, containsKey, containsValue, equals, get, hashCode, isEmpty, keySet, put, putAll, remove, size, values

Methods inherited from interface java.util.SortedMap<K,V>

V> headMap, V> subMap, V> tailMap, firstKey, lastKey, super K> comparator

Method Details

ceilingEntry

public java.util.Map.Entry 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

public 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

descendingKeySet

public NavigableSet 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

descendingMap

public NavigableMap 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

firstEntry

public java.util.Map.Entry 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

floorEntry

public java.util.Map.Entry 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

public 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

headMap

public SortedMap headMap(K toKey)
Equivalent to headMap(toKey, false).

headMap

public NavigableMap 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 - high endpoint of the keys in the returned map
inclusive - true if the high endpoint is to be included in the returned view
Returns:
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

public java.util.Map.Entry 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

public 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

lastEntry

public java.util.Map.Entry 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

lowerEntry

public java.util.Map.Entry 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

public 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

navigableKeySet

public NavigableSet 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

pollFirstEntry

public java.util.Map.Entry 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

public java.util.Map.Entry 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

subMap

public SortedMap subMap(K fromKey,
                             K toKey)
Equivalent to subMap(fromKey, true, toKey, false).

subMap

public NavigableMap 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 fromExclusive and toExclusive 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

tailMap

public SortedMap tailMap(K fromKey)
Equivalent to tailMap(fromKey, true).

tailMap

public NavigableMap 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 - low endpoint of the keys in the returned map
inclusive - true if the low endpoint is to be included in the returned view
Returns:
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