/*
 * Written by Doug Lea with assistance from members of JCP JSR-166
 * Expert Group and released to the public domain, as explained at
 * http://creativecommons.org/licenses/publicdomain
 */

package jsr166x;

import java.util.*;

/**
 * A {@link SortedMap} extended with navigation methods returning
 * key-value pairs holding the closest matches for given search
 * targets. Methods <tt>lowerEntry</tt>, <tt>floorEntry</tt>,
 * <tt>ceilingEntry</tt>, and <tt>higherEntry</tt> return
 * <tt>Map.Entry</tt> objects associated with keys respectively less
 * than, less than or equal, greater than or equal, and greater than a
 * given key, returning <tt>null</tt> if there is no such key.  These
 * methods are designed for locating, not traversing entries. To
 * traverse, use view iterators and/or <tt>submap</tt>. This interface
 * additionally defines methods <tt>firstEntry</tt>,
 * <tt>pollFirstEntry</tt>, <tt>lastEntry</tt>, and
 * <tt>pollLastEntry</tt> that return and/or remove the least and
 * greatest mappings, if any exist, else returning <tt>null</tt>.
 *
 * <p> Implementations of these methods are expected to return
 * <tt>Map.Entry</tt> pairs representing snapshots of mappings at the
 * time they were produced, and thus generally do <em>not</em> support
 * the optional <tt>Entry.setValue</tt> method. Note however that it
 * is possible to change mappings in the associated map using method
 * <tt>put</tt>.
 *
 * @author Doug Lea
 * @param <K> the type of keys maintained by this map
 * @param <V> the type of mapped values 
 */
public interface NavigableMap<K,V> extends SortedMap<K,V> {
    /**
     * Returns a key-value mapping associated with the least key
     * greater than or equal to the given key, or <tt>null</tt> if there is
     * no such entry. 
     * 
     * @param key the key.
     * @return an Entry associated with ceiling of given key, or <tt>null</tt>
     * if there is no such Entry.
     * @throws ClassCastException if key cannot be compared with the keys
     *            currently in the map.
     * @throws NullPointerException if key is <tt>null</tt> and this map
     * does not support <tt>null</tt> keys.
     */
    public Map.Entry<K,V> ceilingEntry(K key);

    /**
     * Returns a key-value mapping associated with the greatest
     * key strictly less than the given key, or <tt>null</tt> if there is no
     * such entry. 
     * 
     * @param key the key.
     * @return an Entry with greatest key less than the given
     * key, or <tt>null</tt> if there is no such Entry.
     * @throws ClassCastException if key cannot be compared with the keys
     *            currently in the map.
     * @throws NullPointerException if key is <tt>null</tt> and this map
     * does not support <tt>null</tt> keys.
     */
    public Map.Entry<K,V> lowerEntry(K key);

    /**
     * Returns a key-value mapping associated with the greatest
     * key less than or equal to the given key, or <tt>null</tt> if there is no
     * such entry. 
     * 
     * @param key the key.
     * @return an Entry associated with floor of given key, or <tt>null</tt>
     * if there is no such Entry.
     * @throws ClassCastException if key cannot be compared with the keys
     *            currently in the map.
     * @throws NullPointerException if key is <tt>null</tt> and this map
     * does not support <tt>null</tt> keys.
     */
    public Map.Entry<K,V> floorEntry(K key);

    /**
     * Returns a key-value mapping associated with the least
     * key strictly greater than the given key, or <tt>null</tt> if there is no
     * such entry. 
     * 
     * @param key the key.
     * @return an Entry with least key greater than the given key, or
     * <tt>null</tt> if there is no such Entry.
     * @throws ClassCastException if key cannot be compared with the keys
     *            currently in the map.
     * @throws NullPointerException if key is <tt>null</tt> and this map
     * does not support <tt>null</tt> keys.
     */
    public Map.Entry<K,V> higherEntry(K key);

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

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

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

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

    /**
     * Returns a view of the portion of this map whose keys range from
     * <tt>fromKey</tt>, inclusive, to <tt>toKey</tt>, exclusive.  (If
     * <tt>fromKey</tt> and <tt>toKey</tt> are equal, the returned sorted map
     * is empty.)  The returned sorted map is backed by this map, so changes
     * in the returned sorted map are reflected in this map, and vice-versa.

     * @param fromKey low endpoint (inclusive) of the subMap.
     * @param toKey high endpoint (exclusive) of the subMap.
     *
     * @return a view of the portion of this map whose keys range from
     * <tt>fromKey</tt>, inclusive, to <tt>toKey</tt>, exclusive.
     *
     * @throws ClassCastException if <tt>fromKey</tt> and
     * <tt>toKey</tt> cannot be compared to one another using this
     * map's comparator (or, if the map has no comparator, using
     * natural ordering).
     * @throws IllegalArgumentException if <tt>fromKey</tt> is greater
     * than <tt>toKey</tt>.
     * @throws NullPointerException if <tt>fromKey</tt> or
     * <tt>toKey</tt> is <tt>null</tt> and this map does not support
     * <tt>null</tt> keys.
     */
    public NavigableMap<K,V> subMap(K fromKey, K toKey);

    /**
     * Returns a view of the portion of this map whose keys are strictly less
     * than <tt>toKey</tt>.  The returned sorted map is backed by this map, so
     * changes in the returned sorted map are reflected in this map, and
     * vice-versa.  
     * @param toKey high endpoint (exclusive) of the headMap.
     * @return a view of the portion of this map whose keys are strictly
     *                less than <tt>toKey</tt>.
     *
     * @throws ClassCastException if <tt>toKey</tt> is not compatible
     *         with this map's comparator (or, if the map has no comparator,
     *         if <tt>toKey</tt> does not implement <tt>Comparable</tt>).
     * @throws NullPointerException if <tt>toKey</tt> is <tt>null</tt>
     * and this map does not support <tt>null</tt> keys.
     */
    public NavigableMap<K,V> headMap(K toKey);

    /**
     * Returns a view of the portion of this map whose keys are
     * greater than or equal to <tt>fromKey</tt>.  The returned sorted
     * map is backed by this map, so changes in the returned sorted
     * map are reflected in this map, and vice-versa.
     * @param fromKey low endpoint (inclusive) of the tailMap.
     * @return a view of the portion of this map whose keys are greater
     *                than or equal to <tt>fromKey</tt>.
     * @throws ClassCastException if <tt>fromKey</tt> is not compatible
     *         with this map's comparator (or, if the map has no comparator,
     *         if <tt>fromKey</tt> does not implement <tt>Comparable</tt>).
     * @throws NullPointerException if <tt>fromKey</tt> is <tt>null</tt>
     * and this map does not support <tt>null</tt> keys.
     */
    public NavigableMap<K,V>  tailMap(K fromKey);
}