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	/*
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation. Oracle designates this
	* particular file as subject to the "Classpath" exception as provided
	* by Oracle in the LICENSE file that accompanied this code.
	*
	* This code is distributed in the hope that it will be useful, but WITHOUT
	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
	* version 2 for more details (a copy is included in the LICENSE file that
	* accompanied this code).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/

	/*
	* This file is available under and governed by the GNU General Public
	* License version 2 only, as published by the Free Software Foundation.
	* However, the following notice accompanied the original version of this
	* file:
	*
	* Written by Doug Lea and Josh Bloch with assistance from members of JCP
	* JSR-166 Expert Group and released to the public domain, as explained at
	* http://creativecommons.org/publicdomain/zero/1.0/
	*/

	package java.util;

	/**
	* A {@link SortedMap} extended with navigation methods returning the
	* closest matches for given search targets. Methods
	* {@link #lowerEntry}, {@link #floorEntry}, {@link #ceilingEntry},
	* and {@link #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
	* {@link #lowerKey}, {@link #floorKey}, {@link #ceilingKey}, and
	* {@link #higherKey} return only the associated keys. All of these
	* methods are designed for locating, not traversing entries.
	*
	* <p>A {@code NavigableMap} may be accessed and traversed in either
	* ascending or descending key order. The {@link #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
	* {@link #subMap(Object, boolean, Object, boolean) subMap(K, boolean, K, boolean)},
	* {@link #headMap(Object, boolean) headMap(K, boolean)}, and
	* {@link #tailMap(Object, boolean) tailMap(K, boolean)}
	* 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.
	*
	* <p>This interface additionally defines methods {@link #firstEntry},
	* {@link #pollFirstEntry}, {@link #lastEntry}, and
	* {@link #pollLastEntry} that return and/or remove the least and
	* greatest mappings, if any exist, else returning {@code null}.
	*
	* <p>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 <em>not</em>
	* support the optional {@code Entry.setValue} method. Note however
	* that it is possible to change mappings in the associated map using
	* method {@code put}.
	*
	* <p>Methods
	* {@link #subMap(Object, Object) subMap(K, K)},
	* {@link #headMap(Object) headMap(K)}, and
	* {@link #tailMap(Object) 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,
	* {@link #keySet()} can be overridden to return {@link NavigableSet}.
	*
	* <p>This interface is a member of the
	* <a href="{@docRoot}/java.base/java/util/package-summary.html#CollectionsFramework">
	* Java Collections Framework</a>.
	*
	* @author Doug Lea
	* @author Josh Bloch
	* @param <K> the type of keys maintained by this map
	* @param <V> the type of mapped values
	* @since 1.6
	*/
	public interface NavigableMap<K,V> extends SortedMap<K,V> {
	/**
	* 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.
	*
	* @param key the key
	* @return 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
	* @throws NullPointerException if the specified key is null
	* and this map does not permit null keys
	*/
	Map.Entry<K,V> lowerEntry(K key);

	/**
	* Returns the greatest key strictly less than the given key, or
	* {@code null} if there is no such key.
	*
	* @param key the key
	* @return 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
	* @throws NullPointerException if the specified key is null
	* and this map does not permit null keys
	*/
	K lowerKey(K 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.
	*
	* @param key the key
	* @return 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
	* @throws NullPointerException if the specified key is null
	* and this map does not permit null keys
	*/
	Map.Entry<K,V> floorEntry(K key);

	/**
	* Returns the greatest key less than or equal to the given key,
	* or {@code null} if there is no such key.
	*
	* @param key the key
	* @return 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
	* @throws NullPointerException if the specified key is null
	* and this map does not permit null keys
	*/
	K floorKey(K 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.
	*
	* @param key the key
	* @return 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
	* @throws NullPointerException if the specified key is null
	* and this map does not permit null keys
	*/
	Map.Entry<K,V> ceilingEntry(K key);

	/**
	* Returns the least key greater than or equal to the given key,
	* or {@code null} if there is no such key.
	*
	* @param key the key
	* @return 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
	* @throws NullPointerException if the specified key is null
	* and this map does not permit null keys
	*/
	K ceilingKey(K 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.
	*
	* @param key the key
	* @return 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
	* @throws NullPointerException if the specified key is null
	* and this map does not permit null keys
	*/
	Map.Entry<K,V> higherEntry(K key);

	/**
	* Returns the least key strictly greater than the given key, or
	* {@code null} if there is no such key.
	*
	* @param key the key
	* @return 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
	* @throws NullPointerException if the specified key is null
	* and this map does not permit null keys
	*/
	K higherKey(K key);

	/**
	* Returns a key-value mapping associated with the least
	* key in this map, or {@code null} if the map is empty.
	*
	* @return an entry with the least key,
	* or {@code null} if this map is empty
	*/
	Map.Entry<K,V> firstEntry();

	/**
	* Returns a key-value mapping associated with the greatest
	* key in this map, or {@code null} if the map is empty.
	*
	* @return an entry with the greatest key,
	* or {@code null} if this map is empty
	*/
	Map.Entry<K,V> lastEntry();

	/**
	* Removes and returns a key-value mapping associated with
	* the least key in this map, or {@code null} if the map is empty.
	*
	* @return the removed first entry of this map,
	* or {@code null} if this map is empty
	*/
	Map.Entry<K,V> pollFirstEntry();

	/**
	* Removes and returns a key-value mapping associated with
	* the greatest key in this map, or {@code null} if the map is empty.
	*
	* @return the removed last entry of this map,
	* or {@code null} if this map is empty
	*/
	Map.Entry<K,V> pollLastEntry();

	/**
	* 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.
	*
	* <p>The returned map has an ordering equivalent to
	* {@link Collections#reverseOrder(Comparator) Collections.reverseOrder}{@code (comparator())}.
	* The expression {@code m.descendingMap().descendingMap()} returns a
	* view of {@code m} essentially equivalent to {@code m}.
	*
	* @return a reverse order view of this map
	*/
	NavigableMap<K,V> descendingMap();

	/**
	* Returns a {@link 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.
	*
	* @return a navigable set view of the keys in this map
	*/
	NavigableSet<K> navigableKeySet();

	/**
	* Returns a reverse order {@link 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.
	*
	* @return a reverse order navigable set view of the keys in this map
	*/
	NavigableSet<K> descendingKeySet();

	/**
	* 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 fromInclusive} and {@code toInclusive} 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.
	*
	* <p>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.
	*
	* @param fromKey low endpoint of the keys in the returned map
	* @param fromInclusive {@code true} if the low endpoint
	* is to be included in the returned view
	* @param toKey high endpoint of the keys in the returned map
	* @param toInclusive {@code true} if the high endpoint
	* is to be included in the returned view
	* @return 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.
	* @throws NullPointerException if {@code fromKey} or {@code toKey}
	* is null and this map does not permit null keys
	* @throws 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
	*/
	NavigableMap<K,V> subMap(K fromKey, boolean fromInclusive,
	K toKey, boolean toInclusive);

	/**
	* 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.
	*
	* <p>The returned map will throw an {@code IllegalArgumentException}
	* on an attempt to insert a key outside its range.
	*
	* @param toKey high endpoint of the keys in the returned map
	* @param inclusive {@code true} if the high endpoint
	* is to be included in the returned view
	* @return 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 {@link Comparable}).
	* Implementations may, but are not required to, throw this
	* exception if {@code toKey} cannot be compared to keys
	* currently in the map.
	* @throws NullPointerException if {@code toKey} is null
	* and this map does not permit null keys
	* @throws IllegalArgumentException if this map itself has a
	* restricted range, and {@code toKey} lies outside the
	* bounds of the range
	*/
	NavigableMap<K,V> headMap(K toKey, 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.
	*
	* <p>The returned map will throw an {@code IllegalArgumentException}
	* on an attempt to insert a key outside its range.
	*
	* @param fromKey low endpoint of the keys in the returned map
	* @param inclusive {@code true} if the low endpoint
	* is to be included in the returned view
	* @return 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 {@link Comparable}).
	* Implementations may, but are not required to, throw this
	* exception if {@code fromKey} cannot be compared to keys
	* currently in the map.
	* @throws NullPointerException if {@code fromKey} is null
	* and this map does not permit null keys
	* @throws IllegalArgumentException if this map itself has a
	* restricted range, and {@code fromKey} lies outside the
	* bounds of the range
	*/
	NavigableMap<K,V> tailMap(K fromKey, boolean inclusive);

	/**
	* {@inheritDoc}
	*
	* <p>Equivalent to {@code subMap(fromKey, true, toKey, false)}.
	*
	* @throws ClassCastException {@inheritDoc}
	* @throws NullPointerException {@inheritDoc}
	* @throws IllegalArgumentException {@inheritDoc}
	*/
	SortedMap<K,V> subMap(K fromKey, K toKey);

	/**
	* {@inheritDoc}
	*
	* <p>Equivalent to {@code headMap(toKey, false)}.
	*
	* @throws ClassCastException {@inheritDoc}
	* @throws NullPointerException {@inheritDoc}
	* @throws IllegalArgumentException {@inheritDoc}
	*/
	SortedMap<K,V> headMap(K toKey);

	/**
	* {@inheritDoc}
	*
	* <p>Equivalent to {@code tailMap(fromKey, true)}.
	*
	* @throws ClassCastException {@inheritDoc}
	* @throws NullPointerException {@inheritDoc}
	* @throws IllegalArgumentException {@inheritDoc}
	*/
	SortedMap<K,V> tailMap(K fromKey);
	}

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