java.util

Interface SortedMap<K,V>

All Superinterfaces:
Map<K,V>
Known Subinterfaces:
ConcurrentNavigableMap<K,V>, NavigableMap<K,V>
Known Implementing Classes:
ConcurrentSkipListMap<K,V>, TreeMap<K,V>

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

A map which guarantees its key's iteration order. The entries in the map are related by the natural ordering of the keys if they are Comparable, or by the provided Comparator. Additional operations take advantage of the sorted nature of the map.

All keys entered in the map must be mutually comparable; in other words, k1.compareTo(k2) or comparator.compare(k1, k2) must not throw a ClassCastException. The ordering must be consistent with equals (see Comparator for this definition), if the map is to obey the general contract of the Map interface. If not, the results are well-defined, but probably not what you wanted.

It is recommended that all implementing classes provide four constructors: 1) one that takes no arguments and builds an empty map sorted by natural order of the keys; 2) one that takes a Comparator for the sorting order; 3) one that takes a Map and sorts according to the natural order of its keys; and 4) one that takes a SortedMap and sorts by the same comparator. Unfortunately, the Java language does not provide a way to enforce this.

Since:
1.2
See Also:
Map, TreeMap, SortedSet, Comparable, Comparator, Collection, ClassCastException

Method Summary

SortedMap
V> headMap(K toKey)
Returns a view of the portion of the map strictly less than toKey.
SortedMap
V> subMap(K fromKey, K toKey)
Returns a view of the portion of the map greater than or equal to fromKey, and strictly less than toKey.
SortedMap
V> tailMap(K fromKey)
Returns a view of the portion of the map greater than or equal to fromKey.
K
firstKey()
Returns the first (lowest sorted) key in the map.
K
lastKey()
Returns the last (highest sorted) key in the map.
Comparator
super K> comparator()
Returns the comparator used in sorting this map, or null if it is the keys' natural ordering.

Methods inherited from interface java.util.Map<K,V>

V>> entrySet, clear, containsKey, containsValue, equals, get, hashCode, isEmpty, keySet, put, putAll, remove, size, values

Method Details

V> headMap

public SortedMapV> headMap(K toKey)
Returns a view of the portion of the map strictly less than toKey. The view is backed by this map, so changes in one show up in the other. The submap supports all optional operations of the original.

The returned map throws an IllegalArgumentException any time a key is used which is out of the range of toKey. Note that the endpoint, toKey, is not included; if you want this value to be included, pass its successor object in to toKey. For example, for Integers, you could request headMap(new Integer(limit.intValue() + 1)).

Parameters:
toKey - the exclusive upper range of the submap
Returns:
the submap
Throws:
ClassCastException - if toKey is not comparable to the map contents
IllegalArgumentException - if this is a subMap, and toKey is out of range
NullPointerException - if toKey is null but the map does not allow null keys

V> subMap

public SortedMapV> subMap(K fromKey,
                              K toKey)
Returns a view of the portion of the map greater than or equal to fromKey, and strictly less than toKey. The view is backed by this map, so changes in one show up in the other. The submap supports all optional operations of the original.

The returned map throws an IllegalArgumentException any time a key is used which is out of the range of fromKey and toKey. Note that the lower endpoint is included, but the upper is not; if you want to change the inclusion or exclusion of an endpoint, pass its successor object in instead. For example, for Integers, you could request subMap(new Integer(lowlimit.intValue() + 1), new Integer(highlimit.intValue() + 1)) to reverse the inclusiveness of both endpoints.

Parameters:
fromKey - the inclusive lower range of the submap
toKey - the exclusive upper range of the submap
Returns:
the submap
Throws:
ClassCastException - if fromKey or toKey is not comparable to the map contents
IllegalArgumentException - if this is a subMap, and fromKey or toKey is out of range
NullPointerException - if fromKey or toKey is null but the map does not allow null keys

V> tailMap

public SortedMapV> tailMap(K fromKey)
Returns a view of the portion of the map greater than or equal to fromKey. The view is backed by this map, so changes in one show up in the other. The submap supports all optional operations of the original.

The returned map throws an IllegalArgumentException any time a key is used which is out of the range of fromKey. Note that the endpoint, fromKey, is included; if you do not want this value to be included, pass its successor object in to fromKey. For example, for Integers, you could request tailMap(new Integer(limit.intValue() + 1)).

Parameters:
fromKey - the inclusive lower range of the submap
Returns:
the submap
Throws:
ClassCastException - if fromKey is not comparable to the map contents
IllegalArgumentException - if this is a subMap, and fromKey is out of range
NullPointerException - if fromKey is null but the map does not allow null keys

firstKey

public K firstKey()
Returns the first (lowest sorted) key in the map.
Returns:
the first key
Throws:
NoSuchElementException - if this map is empty.

lastKey

public K lastKey()
Returns the last (highest sorted) key in the map.
Returns:
the last key
Throws:
NoSuchElementException - if this map is empty.

super K> comparator

public Comparatorsuper K> comparator()
Returns the comparator used in sorting this map, or null if it is the keys' natural ordering.
Returns:
the sorting comparator

SortedMap.java -- A map that makes guarantees about the order of its keys Copyright (C) 1998, 2001, 2004, 2005 Free Software Foundation, Inc. This file is part of GNU Classpath. GNU Classpath is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2, or (at your option) any later version. GNU Classpath 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 for more details. You should have received a copy of the GNU General Public License along with GNU Classpath; see the file COPYING. If not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. Linking this library statically or dynamically with other modules is making a combined work based on this library. Thus, the terms and conditions of the GNU General Public License cover the whole combination. As a special exception, the copyright holders of this library give you permission to link this library with independent modules to produce an executable, regardless of the license terms of these independent modules, and to copy and distribute the resulting executable under terms of your choice, provided that you also meet, for each linked independent module, the terms and conditions of the license of that module. An independent module is a module which is not derived from or based on this library. If you modify this library, you may extend this exception to your version of the library, but you are not obligated to do so. If you do not wish to do so, delete this exception statement from your version.