/*
* @(#)SortedMap.java 1.28 06/04/21
*
* Copyright 2006 Sun Microsystems, Inc. All rights reserved.
* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*/
package java.util;
/**
* A {@link Map} that further provides a <i>total ordering</i> 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
* <tt>entrySet</tt>, <tt>keySet</tt> and <tt>values</tt> 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 <tt>Comparable</tt>
* interface (or be accepted by the specified comparator). Furthermore, all
* such keys must be <i>mutually comparable</i>: <tt>k1.compareTo(k2)</tt> (or
* <tt>comparator.compare(k1, k2)</tt>) must not throw a
* <tt>ClassCastException</tt> for any keys <tt>k1</tt> and <tt>k2</tt> in
* the sorted map. Attempts to violate this restriction will cause the
* offending method or constructor invocation to throw a
* <tt>ClassCastException</tt>.
*
* <p>Note that the ordering maintained by a sorted map (whether or not an
* explicit comparator is provided) must be <i>consistent with equals</i> if
* the sorted map is to correctly implement the <tt>Map</tt> interface. (See
* the <tt>Comparable</tt> interface or <tt>Comparator</tt> interface for a
* precise definition of <i>consistent with equals</i>.) This is so because
* the <tt>Map</tt> interface is defined in terms of the <tt>equals</tt>
* operation, but a sorted map performs all key comparisons using its
* <tt>compareTo</tt> (or <tt>compare</tt>) 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 <i>is</i> well-defined even if its
* ordering is inconsistent with equals; it just fails to obey the general
* contract of the <tt>Map</tt> interface.
*
* <p>All general-purpose sorted map implementation classes should
* provide four "standard" constructors: 1) A void (no arguments)
* constructor, which creates an empty sorted map sorted according to
* the natural ordering of its keys. 2) A constructor with a
* single argument of type <tt>Comparator</tt>, which creates an empty
* sorted map sorted according to the specified comparator. 3) A
* constructor with a single argument of type <tt>Map</tt>, which
* creates a new map with the same key-value mappings as its argument,
* sorted according to the keys' natural ordering. 4) A constructor
* with a single argument of type <tt>SortedMap</tt>,
* which creates a new sorted map with the same key-value mappings and
* the same ordering as the input sorted map. There is no way to
* enforce this recommendation, as interfaces cannot contain
* constructors.
*
* <p>Note: several methods return submaps with restricted key ranges.
* Such ranges are <i>half-open</i>, that is, they include their low
* endpoint but not their high endpoint (where applicable). If you need a
* <i>closed range</i> (which includes both endpoints), and the key type
* allows for calculation of the successor of a given key, merely request
* the subrange from <tt>lowEndpoint</tt> to
* <tt>successor(highEndpoint)</tt>. For example, suppose that <tt>m</tt>
* is a map whose keys are strings. The following idiom obtains a view
* containing all of the key-value mappings in <tt>m</tt> whose keys are
* between <tt>low</tt> and <tt>high</tt>, inclusive:<pre>
* SortedMap<String, V> sub = m.subMap(low, high+"\0");</pre>
*
* A similar technique can be used to generate an <i>open range</i>
* (which contains neither endpoint). The following idiom obtains a
* view containing all of the key-value mappings in <tt>m</tt> whose keys
* are between <tt>low</tt> and <tt>high</tt>, exclusive:<pre>
* SortedMap<String, V> sub = m.subMap(low+"\0", high);</pre>
*
* <p>This interface is a member of the
* <a href="{@docRoot}/../technotes/guides/collections/index.html">
* Java Collections Framework</a>.
*
* @param <K> the type of keys maintained by this map
* @param <V> the type of mapped values
*
* @author Josh Bloch
* @version 1.28, 04/21/06
* @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
* <tt>null</tt> if this map uses the {@linkplain Comparable
* natural ordering} of its keys.
*
* @return the comparator used to order the keys in this map,
* or <tt>null</tt> 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
* <tt>fromKey</tt>, inclusive, to <tt>toKey</tt>, exclusive. (If
* <tt>fromKey</tt> and <tt>toKey</tt> 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 <tt>IllegalArgumentException</tt>
* 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
* <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).
* Implementations may, but are not required to, throw this
* exception if <tt>fromKey</tt> or <tt>toKey</tt>
* cannot be compared to keys currently in the map.
* @throws NullPointerException if <tt>fromKey</tt> or <tt>toKey</tt>
* is null and this map does not permit null keys
* @throws IllegalArgumentException if <tt>fromKey</tt> is greater than
* <tt>toKey</tt>; or if this map itself has a restricted
* range, and <tt>fromKey</tt> or <tt>toKey</tt> 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 <tt>toKey</tt>. 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 <tt>IllegalArgumentException</tt>
* 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 <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 {@link Comparable}).
* Implementations may, but are not required to, throw this
* exception if <tt>toKey</tt> cannot be compared to keys
* currently in the map.
* @throws NullPointerException if <tt>toKey</tt> is null and
* this map does not permit null keys
* @throws IllegalArgumentException if this map itself has a
* restricted range, and <tt>toKey</tt> 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 <tt>fromKey</tt>. 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 <tt>IllegalArgumentException</tt>
* 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 <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 {@link Comparable}).
* Implementations may, but are not required to, throw this
* exception if <tt>fromKey</tt> cannot be compared to keys
* currently in the map.
* @throws NullPointerException if <tt>fromKey</tt> is null and
* this map does not permit null keys
* @throws IllegalArgumentException if this map itself has a
* restricted range, and <tt>fromKey</tt> 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 <tt>remove</tt> operation), the results of
* the iteration are undefined. The set supports element removal,
* which removes the corresponding mapping from the map, via the
* <tt>Iterator.remove</tt>, <tt>Set.remove</tt>,
* <tt>removeAll</tt>, <tt>retainAll</tt>, and <tt>clear</tt>
* operations. It does not support the <tt>add</tt> or <tt>addAll</tt>
* 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 <tt>remove</tt> operation),
* the results of the iteration are undefined. The collection
* supports element removal, which removes the corresponding
* mapping from the map, via the <tt>Iterator.remove</tt>,
* <tt>Collection.remove</tt>, <tt>removeAll</tt>,
* <tt>retainAll</tt> and <tt>clear</tt> operations. It does not
* support the <tt>add</tt> or <tt>addAll</tt> 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 <tt>remove</tt> operation, or through the
* <tt>setValue</tt> 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 <tt>Iterator.remove</tt>,
* <tt>Set.remove</tt>, <tt>removeAll</tt>, <tt>retainAll</tt> and
* <tt>clear</tt> operations. It does not support the
* <tt>add</tt> or <tt>addAll</tt> operations.
*
* @return a set view of the mappings contained in this map,
* sorted in ascending key order
*/
Set<Map.Entry<K, V>> entrySet();
}
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