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
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
- 
Method SummaryModifier and TypeMethodDescriptionceilingEntry(K key) Returns a key-value mapping associated with the least key greater than or equal to the given key, ornullif there is no such key.ceilingKey(K key) Returns the least key greater than or equal to the given key, ornullif there is no such key.Returns a reverse orderNavigableSetview of the keys contained in this map.Returns a reverse order view of the mappings contained in this map.Returns a key-value mapping associated with the least key in this map, ornullif the map is empty.floorEntry(K key) Returns a key-value mapping associated with the greatest key less than or equal to the given key, ornullif there is no such key.Returns the greatest key less than or equal to the given key, ornullif there is no such key.Returns a view of the portion of this map whose keys are strictly less thantoKey.Returns a view of the portion of this map whose keys are less than (or equal to, ifinclusiveis true)toKey.higherEntry(K key) Returns a key-value mapping associated with the least key strictly greater than the given key, ornullif there is no such key.Returns the least key strictly greater than the given key, ornullif there is no such key.Returns a key-value mapping associated with the greatest key in this map, ornullif the map is empty.lowerEntry(K key) Returns a key-value mapping associated with the greatest key strictly less than the given key, ornullif there is no such key.Returns the greatest key strictly less than the given key, ornullif there is no such key.Returns aNavigableSetview of the keys contained in this map.Removes and returns a key-value mapping associated with the least key in this map, ornullif the map is empty (optional operation).Removes and returns a key-value mapping associated with the greatest key in this map, ornullif the map is empty (optional operation).default NavigableMap<K, V> reversed()Returns a reverse-ordered view of this map.Returns a view of the portion of this map whose keys range fromfromKeytotoKey.Returns a view of the portion of this map whose keys range fromfromKey, inclusive, totoKey, exclusive.Returns a view of the portion of this map whose keys are greater than or equal tofromKey.Returns a view of the portion of this map whose keys are greater than (or equal to, ifinclusiveis true)fromKey.Methods declared in interface java.util.Mapclear, compute, computeIfAbsent, computeIfPresent, containsKey, containsValue, equals, forEach, get, getOrDefault, hashCode, isEmpty, merge, put, putAll, putIfAbsent, remove, remove, replace, replace, replaceAll, sizeMethods declared in interface java.util.SequencedMapsequencedEntrySet, sequencedKeySet, sequencedValues
- 
Method Details- 
lowerEntryReturns a key-value mapping associated with the greatest key strictly less than the given key, ornullif there is no such key.- Parameters:
- key- the key
- Returns:
- an entry with the greatest key less than key, ornullif 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
 
- 
lowerKeyReturns the greatest key strictly less than the given key, ornullif there is no such key.- Parameters:
- key- the key
- Returns:
- the greatest key less than key, ornullif 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
 
- 
floorEntryReturns a key-value mapping associated with the greatest key less than or equal to the given key, ornullif there is no such key.- Parameters:
- key- the key
- Returns:
- an entry with the greatest key less than or equal to
         key, ornullif 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
 
- 
floorKeyReturns the greatest key less than or equal to the given key, ornullif there is no such key.- Parameters:
- key- the key
- Returns:
- the greatest key less than or equal to key, ornullif 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
 
- 
ceilingEntryReturns a key-value mapping associated with the least key greater than or equal to the given key, ornullif there is no such key.- Parameters:
- key- the key
- Returns:
- an entry with the least key greater than or equal to
         key, ornullif 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
 
- 
ceilingKeyReturns the least key greater than or equal to the given key, ornullif there is no such key.- Parameters:
- key- the key
- Returns:
- the least key greater than or equal to key, ornullif 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
 
- 
higherEntryReturns a key-value mapping associated with the least key strictly greater than the given key, ornullif there is no such key.- Parameters:
- key- the key
- Returns:
- an entry with the least key greater than key, ornullif 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
 
- 
higherKeyReturns the least key strictly greater than the given key, ornullif there is no such key.- Parameters:
- key- the key
- Returns:
- the least key greater than key, ornullif 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
 
- 
firstEntryReturns a key-value mapping associated with the least key in this map, ornullif the map is empty.- Specified by:
- firstEntryin interface- SequencedMap<K,- V> 
- Returns:
- an entry with the least key,
         or nullif this map is empty
 
- 
lastEntry
- 
pollFirstEntryRemoves and returns a key-value mapping associated with the least key in this map, ornullif the map is empty (optional operation).- Specified by:
- pollFirstEntryin interface- SequencedMap<K,- V> 
- Returns:
- the removed first entry of this map,
         or nullif this map is empty
- Throws:
- UnsupportedOperationException- if the- pollFirstEntryoperation is not supported by this map
 
- 
pollLastEntryRemoves and returns a key-value mapping associated with the greatest key in this map, ornullif the map is empty (optional operation).- Specified by:
- pollLastEntryin interface- SequencedMap<K,- V> 
- Returns:
- the removed last entry of this map,
         or nullif this map is empty
- Throws:
- UnsupportedOperationException- if the- pollLastEntryoperation is not supported by this map
 
- 
descendingMapNavigableMap<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 ownremoveoperation), the results of the iteration are undefined.The returned map has an ordering equivalent to Collections.reverseOrder(comparator()). The expressionm.descendingMap().descendingMap()returns a view ofmessentially equivalent tom.- Returns:
- a reverse order view of this map
 
- 
descendingKeySetNavigableSet<K> descendingKeySet()Returns a reverse orderNavigableSetview 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 ownremoveoperation), the results of the iteration are undefined. The set supports element removal, which removes the corresponding mapping from the map, via theIterator.remove,Set.remove,removeAll,retainAll, andclearoperations. It does not support theaddoraddAlloperations.- Returns:
- a reverse order navigable set view of the keys in this map
 
- 
subMapReturns a view of the portion of this map whose keys range fromfromKeytotoKey. IffromKeyandtoKeyare equal, the returned map is empty unlessfromInclusiveandtoInclusiveare 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 IllegalArgumentExceptionon 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-- trueif the low endpoint is to be included in the returned view
- toKey- high endpoint of the keys in the returned map
- toInclusive-- trueif the high endpoint is to be included in the returned view
- Returns:
- a view of the portion of this map whose keys range from
         fromKeytotoKey
- Throws:
- ClassCastException- if- fromKeyand- toKeycannot 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- fromKeyor- toKeycannot be compared to keys currently in the map.
- NullPointerException- if- fromKeyor- toKeyis null and this map does not permit null keys
- IllegalArgumentException- if- fromKeyis greater than- toKey; or if this map itself has a restricted range, and- fromKeyor- toKeylies outside the bounds of the range
 
- 
headMapReturns a view of the portion of this map whose keys are less than (or equal to, ifinclusiveis 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 IllegalArgumentExceptionon an attempt to insert a key outside its range.- Parameters:
- toKey- high endpoint of the keys in the returned map
- inclusive-- trueif 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 inclusiveis true)toKey
- Throws:
- ClassCastException- if- toKeyis not compatible with this map's comparator (or, if the map has no comparator, if- toKeydoes not implement- Comparable). Implementations may, but are not required to, throw this exception if- toKeycannot be compared to keys currently in the map.
- NullPointerException- if- toKeyis null and this map does not permit null keys
- IllegalArgumentException- if this map itself has a restricted range, and- toKeylies outside the bounds of the range
 
- 
tailMapReturns a view of the portion of this map whose keys are greater than (or equal to, ifinclusiveis 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 IllegalArgumentExceptionon an attempt to insert a key outside its range.- Parameters:
- fromKey- low endpoint of the keys in the returned map
- inclusive-- trueif 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 inclusiveis true)fromKey
- Throws:
- ClassCastException- if- fromKeyis not compatible with this map's comparator (or, if the map has no comparator, if- fromKeydoes not implement- Comparable). Implementations may, but are not required to, throw this exception if- fromKeycannot be compared to keys currently in the map.
- NullPointerException- if- fromKeyis null and this map does not permit null keys
- IllegalArgumentException- if this map itself has a restricted range, and- fromKeylies outside the bounds of the range
 
- 
subMapReturns a view of the portion of this map whose keys range fromfromKey, inclusive, totoKey, exclusive. (IffromKeyandtoKeyare 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 IllegalArgumentExceptionon an attempt to insert a key outside its range.Equivalent to subMap(fromKey, true, toKey, false).- Specified by:
- subMapin interface- SortedMap<K,- V> 
- Parameters:
- fromKey- low endpoint (inclusive) of the keys in the returned map
- toKey- high endpoint (exclusive) of the keys in the returned map
- Returns:
- a view of the portion of this map whose keys range from
         fromKey, inclusive, totoKey, exclusive
- Throws:
- ClassCastException- if- fromKeyand- toKeycannot 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- fromKeyor- toKeycannot be compared to keys currently in the map.
- NullPointerException- if- fromKeyor- toKeyis null and this map does not permit null keys
- IllegalArgumentException- if- fromKeyis greater than- toKey; or if this map itself has a restricted range, and- fromKeyor- toKeylies outside the bounds of the range
 
- 
headMapReturns a view of the portion of this map whose keys are strictly less thantoKey. 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 IllegalArgumentExceptionon an attempt to insert a key outside its range.Equivalent to headMap(toKey, false).- Specified by:
- headMapin interface- SortedMap<K,- V> 
- Parameters:
- toKey- high endpoint (exclusive) of the keys in the returned map
- Returns:
- a view of the portion of this map whose keys are strictly
         less than toKey
- Throws:
- ClassCastException- if- toKeyis not compatible with this map's comparator (or, if the map has no comparator, if- toKeydoes not implement- Comparable). Implementations may, but are not required to, throw this exception if- toKeycannot be compared to keys currently in the map.
- NullPointerException- if- toKeyis null and this map does not permit null keys
- IllegalArgumentException- if this map itself has a restricted range, and- toKeylies outside the bounds of the range
 
- 
tailMapReturns a view of the portion of this map whose keys are greater than or equal tofromKey. 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 IllegalArgumentExceptionon an attempt to insert a key outside its range.Equivalent to tailMap(fromKey, true).- Specified by:
- tailMapin interface- SortedMap<K,- V> 
- Parameters:
- fromKey- low endpoint (inclusive) of the keys in the returned map
- Returns:
- a view of the portion of this map whose keys are greater
         than or equal to fromKey
- Throws:
- ClassCastException- if- fromKeyis not compatible with this map's comparator (or, if the map has no comparator, if- fromKeydoes not implement- Comparable). Implementations may, but are not required to, throw this exception if- fromKeycannot be compared to keys currently in the map.
- NullPointerException- if- fromKeyis null and this map does not permit null keys
- IllegalArgumentException- if this map itself has a restricted range, and- fromKeylies outside the bounds of the range
 
- 
reversedReturns a reverse-ordered view of this map. The encounter order of mappings in the returned view is the inverse of the encounter order of mappings in this map. The reverse ordering affects all order-sensitive operations, including those on the view collections of the returned view. If the implementation permits modifications to this view, the modifications "write through" to the underlying map. Changes to the underlying map might or might not be visible in this reversed view, depending upon the implementation.This method is equivalent to descendingMap.
 
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