edu.emory.mathcs.backport.java.util
Interface NavigableMap

All Superinterfaces:
java.util.Map, java.util.SortedMap
All Known Subinterfaces:
ConcurrentNavigableMap
All Known Implementing Classes:
ConcurrentSkipListMap, TreeMap

public interface NavigableMap
extends java.util.SortedMap

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 viewed and traversed in either ascending or descending key order. The Map methods keySet and entrySet return ascending views, and the additional methods descendingKeySet and descendingEntrySet return descending views. The performance of ascending traversals is likely to be faster than descending traversals. Notice that it is possible to perform subrange traversals in either direction using navigableSubMap. Methods navigableSubMap, navigableHeadMap, and navigableTailMap differ from the similarly named SortedMap methods only in their declared return types. 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.

This interface is a member of the Java Collections Framework.

Since:
1.6
Author:
Doug Lea

Nested Class Summary
 
Nested classes inherited from class java.util.Map
java.util.Map.Entry
 
Method Summary
 java.util.Map.Entry ceilingEntry(java.lang.Object 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.
 java.lang.Object ceilingKey(java.lang.Object key)
          Returns the least key greater than or equal to the given key, or null if there is no such key.
 java.util.Set descendingEntrySet()
          Returns a Set view of the mappings contained in this map.
 java.util.Set descendingKeySet()
          Returns a Set view of the keys 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(java.lang.Object 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.
 java.lang.Object floorKey(java.lang.Object key)
          Returns the greatest key less than or equal to the given key, or null if there is no such key.
 java.util.Map.Entry higherEntry(java.lang.Object 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.
 java.lang.Object higherKey(java.lang.Object 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(java.lang.Object 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.
 java.lang.Object lowerKey(java.lang.Object key)
          Returns the greatest key strictly less than the given key, or null if there is no such key.
 NavigableMap navigableHeadMap(java.lang.Object toKey)
          Returns a view of the portion of this map whose keys are strictly less than toKey.
 NavigableMap navigableSubMap(java.lang.Object fromKey, java.lang.Object toKey)
          Returns a view of the portion of this map whose keys range from fromKey, inclusive, to toKey, exclusive.
 NavigableMap navigableTailMap(java.lang.Object fromKey)
          Returns a view of the portion of this map whose keys are greater than or equal to fromKey.
 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.
 
Methods inherited from interface java.util.SortedMap
comparator, firstKey, headMap, lastKey, subMap, tailMap
 
Methods inherited from interface java.util.Map
clear, containsKey, containsValue, entrySet, equals, get, hashCode, isEmpty, keySet, put, putAll, remove, size, values
 

Method Detail

lowerEntry

public java.util.Map.Entry lowerEntry(java.lang.Object 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:
java.lang.ClassCastException - if the specified key cannot be compared with the keys currently in the map
java.lang.NullPointerException - if the specified key is null and this map does not permit null keys

lowerKey

public java.lang.Object lowerKey(java.lang.Object 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:
java.lang.ClassCastException - if the specified key cannot be compared with the keys currently in the map
java.lang.NullPointerException - if the specified key is null and this map does not permit null keys

floorEntry

public java.util.Map.Entry floorEntry(java.lang.Object 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:
java.lang.ClassCastException - if the specified key cannot be compared with the keys currently in the map
java.lang.NullPointerException - if the specified key is null and this map does not permit null keys

floorKey

public java.lang.Object floorKey(java.lang.Object 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:
java.lang.ClassCastException - if the specified key cannot be compared with the keys currently in the map
java.lang.NullPointerException - if the specified key is null and this map does not permit null keys

ceilingEntry

public java.util.Map.Entry ceilingEntry(java.lang.Object 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:
java.lang.ClassCastException - if the specified key cannot be compared with the keys currently in the map
java.lang.NullPointerException - if the specified key is null and this map does not permit null keys

ceilingKey

public java.lang.Object ceilingKey(java.lang.Object 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:
java.lang.ClassCastException - if the specified key cannot be compared with the keys currently in the map
java.lang.NullPointerException - if the specified key is null and this map does not permit null keys

higherEntry

public java.util.Map.Entry higherEntry(java.lang.Object 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:
java.lang.ClassCastException - if the specified key cannot be compared with the keys currently in the map
java.lang.NullPointerException - if the specified key is null and this map does not permit null keys

higherKey

public java.lang.Object higherKey(java.lang.Object 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:
java.lang.ClassCastException - if the specified key cannot be compared with the keys currently in the map
java.lang.NullPointerException - if the specified key is null and this map does not permit null keys

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

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

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

descendingKeySet

public java.util.Set descendingKeySet()
Returns a Set 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 set view of the keys contained in this map, sorted in descending order

descendingEntrySet

public java.util.Set descendingEntrySet()
Returns a Set view of the mappings contained in this map. The set's iterator returns the entries in descending key 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, or through the setValue operation on a map entry returned by the iterator) 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 set view of the mappings contained in this map, sorted in descending key order

navigableSubMap

public NavigableMap navigableSubMap(java.lang.Object fromKey,
                                    java.lang.Object 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.

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, to toKey, exclusive
Throws:
java.lang.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.
java.lang.NullPointerException - if fromKey or toKey is null and this map does not permit null keys
java.lang.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

navigableHeadMap

public NavigableMap navigableHeadMap(java.lang.Object 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.

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:
java.lang.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.
java.lang.NullPointerException - if toKey is null and this map does not permit null keys
java.lang.IllegalArgumentException - if this map itself has a restricted range, and toKey lies outside the bounds of the range

navigableTailMap

public NavigableMap navigableTailMap(java.lang.Object 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.

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:
java.lang.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.
java.lang.NullPointerException - if fromKey is null and this map does not permit null keys
java.lang.IllegalArgumentException - if this map itself has a restricted range, and fromKey lies outside the bounds of the range