edu.emory.mathcs.backport.java.util

Interface NavigableMap

All Superinterfaces:
SortedMap
Known Subinterfaces:
ConcurrentNavigableMap
Known Implementing Classes:
ConcurrentSkipListMap, TreeMap

public interface NavigableMap
extends SortedMap

A java.util.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.

Authors:
Doug Lea
Josh Bloch
Since:
1.6

Method Summary

Map.Entry
ceilingEntry(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.
Object
ceilingKey(Object 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.
Map.Entry
firstEntry()
Returns a key-value mapping associated with the least key in this map, or null if the map is empty.
Map.Entry
floorEntry(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.
Object
floorKey(Object key)
Returns the greatest key less than or equal to the given key, or null if there is no such key.
SortedMap
headMap(Object toKey)
Equivalent to headMap(toKey, false).
NavigableMap
headMap(Object 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.
Map.Entry
higherEntry(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.
Object
higherKey(Object key)
Returns the least key strictly greater than the given key, or null if there is no such key.
Map.Entry
lastEntry()
Returns a key-value mapping associated with the greatest key in this map, or null if the map is empty.
Map.Entry
lowerEntry(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.
Object
lowerKey(Object 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.
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.
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(Object fromKey, Object toKey)
Equivalent to subMap(fromKey, true, toKey, false).
NavigableMap
subMap(Object fromKey, boolean fromInclusive, Object toKey, boolean toInclusive)
Returns a view of the portion of this map whose keys range from fromKey to toKey.
SortedMap
tailMap(Object fromKey)
Equivalent to tailMap(fromKey, true).
NavigableMap
tailMap(Object 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.

Method Details

ceilingEntry

public Map.Entry ceilingEntry(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

ceilingKey

public Object ceilingKey(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

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 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 Map.Entry floorEntry(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

floorKey

public Object floorKey(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

headMap

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

headMap

public NavigableMap headMap(Object 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

higherEntry

public Map.Entry higherEntry(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

higherKey

public Object higherKey(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

lastEntry

public 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 Map.Entry lowerEntry(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

lowerKey

public Object lowerKey(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

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 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 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(Object fromKey,
                        Object toKey)
Equivalent to subMap(fromKey, true, toKey, false).

subMap

public NavigableMap subMap(Object fromKey,
                           boolean fromInclusive,
                           Object 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

tailMap

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

tailMap

public NavigableMap tailMap(Object 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