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package java.util;

/**

 * A {@link Map} that further provides a <em>total ordering</em> on its keys.

 * The map is ordered according to the {@linkplain Comparable natural

 * ordering} of its keys, or by a {@link Comparator} typically

 * provided at sorted map creation time.  This order is reflected when

 * iterating over the sorted map's collection views (returned by the

 * {@code entrySet}, {@code keySet} and {@code values} methods).

 * Several additional operations are provided to take advantage of the

 * ordering.  (This interface is the map analogue of {@link SortedSet}.)

 *

 * <p>All keys inserted into a sorted map must implement the {@code Comparable}

 * interface (or be accepted by the specified comparator).  Furthermore, all

 * such keys must be <em>mutually comparable</em>: {@code k1.compareTo(k2)} (or

 * {@code comparator.compare(k1, k2)}) must not throw a

 * {@code ClassCastException} for any keys {@code k1} and {@code k2} in

 * the sorted map.  Attempts to violate this restriction will cause the

 * offending method or constructor invocation to throw a

 * {@code ClassCastException}.

 *

 * <p>Note that the ordering maintained by a sorted map (whether or not an

 * explicit comparator is provided) must be <em>consistent with equals</em> if

 * the sorted map is to correctly implement the {@code Map} interface.  (See

 * the {@code Comparable} interface or {@code Comparator} interface for a

 * precise definition of <em>consistent with equals</em>.)  This is so because

 * the {@code Map} interface is defined in terms of the {@code equals}

 * operation, but a sorted map performs all key comparisons using its

 * {@code compareTo} (or {@code compare}) method, so two keys that are

 * deemed equal by this method are, from the standpoint of the sorted map,

 * equal.  The behavior of a tree map <em>is</em> well-defined even if its

 * ordering is inconsistent with equals; it just fails to obey the general

 * contract of the {@code Map} interface.

 *

 * <p>All general-purpose sorted map implementation classes should provide four

 * "standard" constructors. It is not possible to enforce this recommendation

 * though as required constructors cannot be specified by interfaces. The

 * expected "standard" constructors for all sorted map implementations are:

 * <ol>

 *   <li>A void (no arguments) constructor, which creates an empty sorted map

 *   sorted according to the natural ordering of its keys.</li>

 *   <li>A constructor with a single argument of type {@code Comparator}, which

 *   creates an empty sorted map sorted according to the specified comparator.</li>

 *   <li>A constructor with a single argument of type {@code Map}, which creates

 *   a new map with the same key-value mappings as its argument, sorted

 *   according to the keys' natural ordering.</li>

 *   <li>A constructor with a single argument of type {@code SortedMap}, which

 *   creates a new sorted map with the same key-value mappings and the same

 *   ordering as the input sorted map.</li>

 * </ol>

 *

 * <p><strong>Note</strong>: several methods return submaps with restricted key

 * ranges. Such ranges are <em>half-open</em>, that is, they include their low

 * endpoint but not their high endpoint (where applicable).  If you need a

 * <em>closed range</em> (which includes both endpoints), and the key type

 * allows for calculation of the successor of a given key, merely request

 * the subrange from {@code lowEndpoint} to

 * {@code successor(highEndpoint)}.  For example, suppose that {@code m}

 * is a map whose keys are strings.  The following idiom obtains a view

 * containing all of the key-value mappings in {@code m} whose keys are

 * between {@code low} and {@code high}, inclusive:<pre>

 *   SortedMap&lt;String, V&gt; sub = m.subMap(low, high+"\0");</pre>

 *

 * A similar technique can be used to generate an <em>open range</em>

 * (which contains neither endpoint).  The following idiom obtains a

 * view containing all of the key-value mappings in {@code m} whose keys

 * are between {@code low} and {@code high}, exclusive:<pre>

 *   SortedMap&lt;String, V&gt; sub = m.subMap(low+"\0", high);</pre>

 *

 * <p>This interface is a member of the

 * <a href="{@docRoot}/java/util/package-summary.html#CollectionsFramework">

 * Java Collections Framework</a>.

 *

 * @param <K> the type of keys maintained by this map

 * @param <V> the type of mapped values

 *

 * @author  Josh Bloch

 * @see Map

 * @see TreeMap

 * @see SortedSet

 * @see Comparator

 * @see Comparable

 * @see Collection

 * @see ClassCastException

 * @since 1.2

 */

public interface SortedMap<K,V> extends Map<K,V> {

    /**

     * Returns the comparator used to order the keys in this map, or

     * {@code null} if this map uses the {@linkplain Comparable

     * natural ordering} of its keys.

     *

     * @return the comparator used to order the keys in this map,

     *         or {@code null} if this map uses the natural ordering

     *         of its keys

     */

    Comparator<? super K> comparator();

    /**

     * Returns a view of the portion of this map whose keys range from

     * {@code fromKey}, inclusive, to {@code toKey}, exclusive.  (If

     * {@code fromKey} and {@code toKey} are equal, the returned map

     * is empty.)  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 (inclusive) of the keys in the returned map

     * @param toKey high endpoint (exclusive) of the keys in the returned map

     * @return a view of the portion of this map whose keys range from

     *         {@code fromKey}, inclusive, to {@code toKey}, exclusive

     * @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

     */

    SortedMap<K,V> subMap(K fromKey, K toKey);

    /**

     * Returns a view of the portion of this map whose keys are

     * strictly less than {@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 (exclusive) of the keys in the returned map

     * @return a view of the portion of this map whose keys are strictly

     *         less than {@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

     */

    SortedMap<K,V> headMap(K toKey);

    /**

     * Returns a view of the portion of this map whose keys are

     * greater than or equal to {@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 (inclusive) of the keys in the returned map

     * @return a view of the portion of this map whose keys are greater

     *         than or equal to {@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

     */

    SortedMap<K,V> tailMap(K fromKey);

    /**

     * Returns the first (lowest) key currently in this map.

     *

     * @return the first (lowest) key currently in this map

     * @throws NoSuchElementException if this map is empty

     */

    K firstKey();

    /**

     * Returns the last (highest) key currently in this map.

     *

     * @return the last (highest) key currently in this map

     * @throws NoSuchElementException if this map is empty

     */

    K lastKey();

    /**

     * Returns a {@link Set} 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 set view of the keys contained in this map, sorted in

     *         ascending order

     */

    Set<K> keySet();

    /**

     * Returns a {@link Collection} view of the values contained in this map.

     * The collection's iterator returns the values in ascending order

     * of the corresponding keys.

     * The collection is backed by the map, so changes to the map are

     * reflected in the collection, and vice-versa.  If the map is

     * modified while an iteration over the collection is in progress

     * (except through the iterator's own {@code remove} operation),

     * the results of the iteration are undefined.  The collection

     * supports element removal, which removes the corresponding

     * mapping from the map, via the {@code Iterator.remove},

     * {@code Collection.remove}, {@code removeAll},

     * {@code retainAll} and {@code clear} operations.  It does not

     * support the {@code add} or {@code addAll} operations.

     *

     * @return a collection view of the values contained in this map,

     *         sorted in ascending key order

     */

    Collection<V> values();

    /**

     * Returns a {@link Set} view of the mappings contained in this map.

     * The set's iterator returns the entries in ascending key 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, or through the

     * {@code setValue} operation on a map entry returned by the

     * iterator) 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 set view of the mappings contained in this map,

     *         sorted in ascending key order

     */

    Set<Map.Entry<K, V>> entrySet();

}