SortedMap

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java.util
Interface SortedMap

All Superinterfaces:: Map

All Known Implementing Classes:: Collections.SynchronizedSortedMap, Collections.UnmodifiableSortedMap, TreeMap, TreeMap.SubMap

public interface SortedMap
extends Map

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

Nested Class Summary

Nested classes inherited from class java.util.Map

Map.Entry

Method Summary

Comparator comparator()
          Returns the comparator used in sorting this map, or null if it is the keys' natural ordering.

java.lang.Object firstKey()
          Returns the first (lowest sorted) key in the map.

SortedMap headMap(java.lang.Object toKey)
          Returns a view of the portion of the map strictly less than toKey.

java.lang.Object lastKey()
          Returns the last (highest sorted) key in the map.

SortedMap subMap(java.lang.Object fromKey, java.lang.Object toKey)
          Returns a view of the portion of the map greater than or equal to fromKey, and strictly less than toKey.

SortedMap tailMap(java.lang.Object fromKey)
          Returns a view of the portion of the map greater than or equal to fromKey.

Methods inherited from interface java.util.Map

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

Method Detail

comparator

public Comparator comparator()

Returns the comparator used in sorting this map, or null if it is the keys' natural ordering.

firstKey

public java.lang.Object firstKey()

Returns the first (lowest sorted) key in the map.

headMap

public SortedMap headMap(java.lang.Object 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)).

lastKey

public java.lang.Object lastKey()

Returns the last (highest sorted) key in the map.

subMap

public SortedMap subMap(java.lang.Object fromKey,
                        java.lang.Object 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.

tailMap

public SortedMap tailMap(java.lang.Object 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)).