Module java.base
Package java.util

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>,SortedMap<K,V>
All Known Subinterfaces:
ConcurrentNavigableMap<K,V>
All Known Implementing Classes:
ConcurrentSkipListMap,TreeMap
public interfaceNavigableMap<K,V>extendsSortedMap<K,V>
ASortedMap extended with navigation methods returning the closest matches for given search targets. MethodslowerEntry(K),floorEntry(K),ceilingEntry(K), andhigherEntry(K) returnMap.Entry objects associated with keys respectively less than, less than or equal, greater than or equal, and greater than a given key, returningnull if there is no such key. Similarly, methodslowerKey(K),floorKey(K),ceilingKey(K), andhigherKey(K) return only the associated keys. All of these methods are designed for locating, not traversing entries.

ANavigableMap may be accessed and traversed in either ascending or descending key order. ThedescendingMap() 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. MethodssubMap(K, boolean, K, boolean),headMap(K, boolean), andtailMap(K, boolean) differ from the like-namedSortedMap methods in accepting additional arguments describing whether lower and upper bounds are inclusive versus exclusive. Submaps of anyNavigableMap must implement theNavigableMap interface.

This interface additionally defines methodsfirstEntry(),pollFirstEntry(),lastEntry(), andpollLastEntry() that return and/or remove the least and greatest mappings, if any exist, else returningnull.

Implementations of entry-returning methods are expected to returnMap.Entry pairs representing snapshots of mappings at the time they were produced, and thus generally donot support the optionalEntry.setValue method. Note however that it is possible to change mappings in the associated map using methodput.

MethodssubMap(K, K),headMap(K), andtailMap(K) are specified to returnSortedMap to allow existing implementations ofSortedMap to be compatibly retrofitted to implementNavigableMap, but extensions and implementations of this interface are encouraged to override these methods to returnNavigableMap. Similarly,SortedMap.keySet() can be overridden to returnNavigableSet.

This interface is a member of the Java Collections Framework.

Since:
1.6

  • 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, ornull if there is no such key.
      Parameters:
      key - the key
      Returns:
      an entry with the greatest key less thankey, ornull 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, ornull if there is no such key.
      Parameters:
      key - the key
      Returns:
      the greatest key less thankey, ornull 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, ornull if there is no such key.
      Parameters:
      key - the key
      Returns:
      an entry with the greatest key less than or equal tokey, ornull 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, ornull if there is no such key.
      Parameters:
      key - the key
      Returns:
      the greatest key less than or equal tokey, ornull 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, ornull if there is no such key.
      Parameters:
      key - the key
      Returns:
      an entry with the least key greater than or equal tokey, ornull 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, ornull if there is no such key.
      Parameters:
      key - the key
      Returns:
      the least key greater than or equal tokey, ornull 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, ornull if there is no such key.
      Parameters:
      key - the key
      Returns:
      an entry with the least key greater thankey, ornull 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, ornull if there is no such key.
      Parameters:
      key - the key
      Returns:
      the least key greater thankey, ornull 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, ornull if the map is empty.
      Returns:
      an entry with the least key, ornull if this map is empty

    • lastEntry

      Map.Entry<K,V> lastEntry()
      Returns a key-value mapping associated with the greatest key in this map, ornull if the map is empty.
      Returns:
      an entry with the greatest key, ornull 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, ornull if the map is empty.
      Returns:
      the removed first entry of this map, ornull if this map is empty

    • pollLastEntry

      Map.Entry<K,V> pollLastEntry()
      Removes and returns a key-value mapping associated with the greatest key in this map, ornull if the map is empty.
      Returns:
      the removed last entry of this map, ornull if this map is empty

    • 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 ownremove operation), the results of the iteration are undefined.

      The returned map has an ordering equivalent toCollections.reverseOrder(comparator()). The expressionm.descendingMap().descendingMap() returns a view ofm essentially equivalent tom.

      Returns:
      a reverse order view of this map

    • navigableKeySet

      NavigableSet<K> navigableKeySet()
      Returns aNavigableSet 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 theIterator.remove,Set.remove,removeAll,retainAll, andclear operations. It does not support theadd oraddAll operations.
      Returns:
      a navigable set view of the keys in this map

    • descendingKeySet

      NavigableSet<K> descendingKeySet()
      Returns a reverse orderNavigableSet 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 theIterator.remove,Set.remove,removeAll,retainAll, andclear operations. It does not support theadd oraddAll operations.
      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 fromfromKey totoKey. IffromKey andtoKey are equal, the returned map is empty unlessfromInclusive andtoInclusive 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 anIllegalArgumentException 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 fromfromKey totoKey
      Throws:
      ClassCastException - iffromKey andtoKey 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 iffromKey ortoKey cannot be compared to keys currently in the map.
      NullPointerException - iffromKey ortoKey is null and this map does not permit null keys
      IllegalArgumentException - iffromKey is greater thantoKey; or if this map itself has a restricted range, andfromKey ortoKey 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, ifinclusive 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 anIllegalArgumentException 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, ifinclusive is true)toKey
      Throws:
      ClassCastException - iftoKey is not compatible with this map's comparator (or, if the map has no comparator, iftoKey does not implementComparable). Implementations may, but are not required to, throw this exception iftoKey cannot be compared to keys currently in the map.
      NullPointerException - iftoKey is null and this map does not permit null keys
      IllegalArgumentException - if this map itself has a restricted range, andtoKey lies outside the bounds of the range

    • tailMap

      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, ifinclusive 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 anIllegalArgumentException 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, ifinclusive is true)fromKey
      Throws:
      ClassCastException - iffromKey is not compatible with this map's comparator (or, if the map has no comparator, iffromKey does not implementComparable). Implementations may, but are not required to, throw this exception iffromKey cannot be compared to keys currently in the map.
      NullPointerException - iffromKey is null and this map does not permit null keys
      IllegalArgumentException - if this map itself has a restricted range, andfromKey lies outside the bounds of the range

    • subMap

      SortedMap<K,V> subMap(K fromKey,K toKey)
      Returns a view of the portion of this map whose keys range fromfromKey, inclusive, totoKey, exclusive. (IffromKey andtoKey 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 anIllegalArgumentException on an attempt to insert a key outside its range.

      Equivalent tosubMap(fromKey, true, toKey, false).

      Specified by:
      subMap in 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 fromfromKey, inclusive, totoKey, exclusive
      Throws:
      ClassCastException - iffromKey andtoKey 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 iffromKey ortoKey cannot be compared to keys currently in the map.
      NullPointerException - iffromKey ortoKey is null and this map does not permit null keys
      IllegalArgumentException - iffromKey is greater thantoKey; or if this map itself has a restricted range, andfromKey ortoKey lies outside the bounds of the range

    • headMap

      SortedMap<K,V> headMap(K toKey)
      Returns 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 anIllegalArgumentException on an attempt to insert a key outside its range.

      Equivalent toheadMap(toKey, false).

      Specified by:
      headMap in 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 thantoKey
      Throws:
      ClassCastException - iftoKey is not compatible with this map's comparator (or, if the map has no comparator, iftoKey does not implementComparable). Implementations may, but are not required to, throw this exception iftoKey cannot be compared to keys currently in the map.
      NullPointerException - iftoKey is null and this map does not permit null keys
      IllegalArgumentException - if this map itself has a restricted range, andtoKey lies outside the bounds of the range

    • tailMap

      SortedMap<K,V> tailMap(K fromKey)
      Returns 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 anIllegalArgumentException on an attempt to insert a key outside its range.

      Equivalent totailMap(fromKey, true).

      Specified by:
      tailMap in 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 tofromKey
      Throws:
      ClassCastException - iffromKey is not compatible with this map's comparator (or, if the map has no comparator, iffromKey does not implementComparable). Implementations may, but are not required to, throw this exception iffromKey cannot be compared to keys currently in the map.
      NullPointerException - iffromKey is null and this map does not permit null keys
      IllegalArgumentException - if this map itself has a restricted range, andfromKey lies outside the bounds of the range