edu.emory.mathcs.backport.java.util

Interface NavigableMap

public interface NavigableMap extends SortedMap

A java.util.SortedMap extended with navigation methods returning the closest matches for given search targets. Methods {@code lowerEntry}, {@code floorEntry}, {@code ceilingEntry}, and {@code higherEntry} return {@code Map.Entry} objects associated with keys respectively less than, less than or equal, greater than or equal, and greater than a given key, returning {@code null} if there is no such key. Similarly, methods {@code lowerKey}, {@code floorKey}, {@code ceilingKey}, and {@code higherKey} return only the associated keys. All of these methods are designed for locating, not traversing entries.

A {@code NavigableMap} may be accessed and traversed in either ascending or descending key order. The {@code 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 {@code subMap}, {@code headMap}, and {@code tailMap} differ from the like-named {@code SortedMap} methods in accepting additional arguments describing whether lower and upper bounds are inclusive versus exclusive. Submaps of any {@code NavigableMap} must implement the {@code NavigableMap} interface.

This interface additionally defines methods {@code firstEntry}, {@code pollFirstEntry}, {@code lastEntry}, and {@code pollLastEntry} that return and/or remove the least and greatest mappings, if any exist, else returning {@code null}.

Implementations of entry-returning methods are expected to return {@code Map.Entry} pairs representing snapshots of mappings at the time they were produced, and thus generally do not support the optional {@code Entry.setValue} method. Note however that it is possible to change mappings in the associated map using method {@code put}.

Methods subMap(K, K), headMap(K), and tailMap(K) are specified to return {@code SortedMap} to allow existing implementations of {@code SortedMap} to be compatibly retrofitted to implement {@code NavigableMap}, but extensions and implementations of this interface are encouraged to override these methods to return {@code NavigableMap}. Similarly, NavigableMap can be overriden to return {@code NavigableSet}.

This interface is a member of the Java Collections Framework.

Since: 1.6

Author: Doug Lea Josh Bloch

Method Summary
EntryceilingEntry(Object key)
Returns a key-value mapping associated with the least key greater than or equal to the given key, or {@code null} if there is no such key.
ObjectceilingKey(Object key)
Returns the least key greater than or equal to the given key, or {@code null} if there is no such key.
NavigableSetdescendingKeySet()
Returns a reverse order NavigableSet view of the keys contained in this map.
NavigableMapdescendingMap()
Returns a reverse order view of the mappings contained in this map.
EntryfirstEntry()
Returns a key-value mapping associated with the least key in this map, or {@code null} if the map is empty.
EntryfloorEntry(Object key)
Returns a key-value mapping associated with the greatest key less than or equal to the given key, or {@code null} if there is no such key.
ObjectfloorKey(Object key)
Returns the greatest key less than or equal to the given key, or {@code null} if there is no such key.
NavigableMapheadMap(Object toKey, boolean inclusive)
Returns a view of the portion of this map whose keys are less than (or equal to, if {@code inclusive} is true) {@code toKey}.
SortedMapheadMap(Object toKey)
{@inheritDoc }

Equivalent to {@code headMap(toKey, false)}.

EntryhigherEntry(Object key)
Returns a key-value mapping associated with the least key strictly greater than the given key, or {@code null} if there is no such key.
ObjecthigherKey(Object key)
Returns the least key strictly greater than the given key, or {@code null} if there is no such key.
EntrylastEntry()
Returns a key-value mapping associated with the greatest key in this map, or {@code null} if the map is empty.
EntrylowerEntry(Object key)
Returns a key-value mapping associated with the greatest key strictly less than the given key, or {@code null} if there is no such key.
ObjectlowerKey(Object key)
Returns the greatest key strictly less than the given key, or {@code null} if there is no such key.
NavigableSetnavigableKeySet()
Returns a NavigableSet view of the keys contained in this map.
EntrypollFirstEntry()
Removes and returns a key-value mapping associated with the least key in this map, or {@code null} if the map is empty.
EntrypollLastEntry()
Removes and returns a key-value mapping associated with the greatest key in this map, or {@code null} if the map is empty.
NavigableMapsubMap(Object fromKey, boolean fromInclusive, Object toKey, boolean toInclusive)
Returns a view of the portion of this map whose keys range from {@code fromKey} to {@code toKey}.
SortedMapsubMap(Object fromKey, Object toKey)
{@inheritDoc }

Equivalent to {@code subMap(fromKey, true, toKey, false)}.

NavigableMaptailMap(Object fromKey, boolean inclusive)
Returns a view of the portion of this map whose keys are greater than (or equal to, if {@code inclusive} is true) {@code fromKey}.
SortedMaptailMap(Object fromKey)
{@inheritDoc }

Equivalent to {@code tailMap(fromKey, true)}.

Method Detail

ceilingEntry

public Entry ceilingEntry(Object key)
Returns a key-value mapping associated with the least key greater than or equal to the given key, or {@code null} if there is no such key.

Parameters: key the key

Returns: an entry with the least key greater than or equal to {@code key}, or {@code null} 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

public Object ceilingKey(Object key)
Returns the least key greater than or equal to the given key, or {@code null} if there is no such key.

Parameters: key the key

Returns: the least key greater than or equal to {@code key}, or {@code null} 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

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 {@code remove} operation), the results of the iteration are undefined. The set supports element removal, which removes the corresponding mapping from the map, via the {@code Iterator.remove}, {@code Set.remove}, {@code removeAll}, {@code retainAll}, and {@code clear} operations. It does not support the {@code add} or {@code 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 {@code remove} operation), the results of the iteration are undefined.

The returned map has an ordering equivalent to Collections.reverseOrder(comparator()). The expression {@code m.descendingMap().descendingMap()} returns a view of {@code m} essentially equivalent to {@code m}.

Returns: a reverse order view of this map

firstEntry

public Entry firstEntry()
Returns a key-value mapping associated with the least key in this map, or {@code null} if the map is empty.

Returns: an entry with the least key, or {@code null} if this map is empty

floorEntry

public Entry floorEntry(Object key)
Returns a key-value mapping associated with the greatest key less than or equal to the given key, or {@code null} if there is no such key.

Parameters: key the key

Returns: an entry with the greatest key less than or equal to {@code key}, or {@code null} 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

public Object floorKey(Object key)
Returns the greatest key less than or equal to the given key, or {@code null} if there is no such key.

Parameters: key the key

Returns: the greatest key less than or equal to {@code key}, or {@code null} 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

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 {@code inclusive} is true) {@code 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 {@code IllegalArgumentException} on an attempt to insert a key outside its range.

Parameters: toKey high endpoint of the keys in the returned map inclusive {@code 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 {@code inclusive} is true) {@code toKey}

Throws: ClassCastException if {@code toKey} is not compatible with this map's comparator (or, if the map has no comparator, if {@code toKey} does not implement java.lang.Comparable). Implementations may, but are not required to, throw this exception if {@code toKey} cannot be compared to keys currently in the map. NullPointerException if {@code toKey} is null and this map does not permit null keys IllegalArgumentException if this map itself has a restricted range, and {@code toKey} lies outside the bounds of the range

headMap

public SortedMap headMap(Object toKey)
{@inheritDoc }

Equivalent to {@code headMap(toKey, false)}.

Throws: ClassCastException {@inheritDoc } NullPointerException {@inheritDoc } IllegalArgumentException {@inheritDoc }

higherEntry

public Entry higherEntry(Object key)
Returns a key-value mapping associated with the least key strictly greater than the given key, or {@code null} if there is no such key.

Parameters: key the key

Returns: an entry with the least key greater than {@code key}, or {@code null} 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

public Object higherKey(Object key)
Returns the least key strictly greater than the given key, or {@code null} if there is no such key.

Parameters: key the key

Returns: the least key greater than {@code key}, or {@code null} 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

lastEntry

public Entry lastEntry()
Returns a key-value mapping associated with the greatest key in this map, or {@code null} if the map is empty.

Returns: an entry with the greatest key, or {@code null} if this map is empty

lowerEntry

public Entry lowerEntry(Object key)
Returns a key-value mapping associated with the greatest key strictly less than the given key, or {@code null} if there is no such key.

Parameters: key the key

Returns: an entry with the greatest key less than {@code key}, or {@code null} 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

public Object lowerKey(Object key)
Returns the greatest key strictly less than the given key, or {@code null} if there is no such key.

Parameters: key the key

Returns: the greatest key less than {@code key}, or {@code null} 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

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 {@code remove} operation), the results of the iteration are undefined. The set supports element removal, which removes the corresponding mapping from the map, via the {@code Iterator.remove}, {@code Set.remove}, {@code removeAll}, {@code retainAll}, and {@code clear} operations. It does not support the {@code add} or {@code addAll} operations.

Returns: a navigable set view of the keys in this map

pollFirstEntry

public Entry pollFirstEntry()
Removes and returns a key-value mapping associated with the least key in this map, or {@code null} if the map is empty.

Returns: the removed first entry of this map, or {@code null} if this map is empty

pollLastEntry

public Entry pollLastEntry()
Removes and returns a key-value mapping associated with the greatest key in this map, or {@code null} if the map is empty.

Returns: the removed last entry of this map, or {@code null} if this map is empty

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 {@code fromKey} to {@code toKey}. If {@code fromKey} and {@code toKey} are equal, the returned map is empty unless {@code fromExclusive} and {@code 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 {@code 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 {@code true} if the low endpoint is to be included in the returned view toKey high endpoint of the keys in the returned map toInclusive {@code 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 {@code fromKey} to {@code toKey}

Throws: ClassCastException if {@code fromKey} and {@code 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 {@code fromKey} or {@code toKey} cannot be compared to keys currently in the map. NullPointerException if {@code fromKey} or {@code toKey} is null and this map does not permit null keys IllegalArgumentException if {@code fromKey} is greater than {@code toKey}; or if this map itself has a restricted range, and {@code fromKey} or {@code toKey} lies outside the bounds of the range

subMap

public SortedMap subMap(Object fromKey, Object toKey)
{@inheritDoc }

Equivalent to {@code subMap(fromKey, true, toKey, false)}.

Throws: ClassCastException {@inheritDoc } NullPointerException {@inheritDoc } IllegalArgumentException {@inheritDoc }

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 {@code inclusive} is true) {@code 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 {@code IllegalArgumentException} on an attempt to insert a key outside its range.

Parameters: fromKey low endpoint of the keys in the returned map inclusive {@code 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 {@code inclusive} is true) {@code fromKey}

Throws: ClassCastException if {@code fromKey} is not compatible with this map's comparator (or, if the map has no comparator, if {@code fromKey} does not implement java.lang.Comparable). Implementations may, but are not required to, throw this exception if {@code fromKey} cannot be compared to keys currently in the map. NullPointerException if {@code fromKey} is null and this map does not permit null keys IllegalArgumentException if this map itself has a restricted range, and {@code fromKey} lies outside the bounds of the range

tailMap

public SortedMap tailMap(Object fromKey)
{@inheritDoc }

Equivalent to {@code tailMap(fromKey, true)}.

Throws: ClassCastException {@inheritDoc } NullPointerException {@inheritDoc } IllegalArgumentException {@inheritDoc }