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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
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  /*
   * 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;
  
  // BEGIN android-note
  // removed link to collections framework docs
  // END android-note
  
  /**
   * 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}.
   *
   * @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
       */
      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
       */
      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
       */
      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
       */
      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
       */
      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
       */
      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
       */
      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
       */
      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);
  }
  