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 .