java.util
Interface SortedMap<K,V>

All Superinterfaces:
Map sample code for java.util.Map definition code for java.util.Map <K,V>
All Known Implementing Classes:
TreeMap sample code for java.util.TreeMap definition code for java.util.TreeMap

public interface SortedMap<K,V>
extends Map sample code for java.util.Map definition code for java.util.Map <K,V>

A map that further guarantees that it will be in ascending key order, sorted according to the natural ordering of its keys (see the Comparable interface), or by a comparator provided at sorted map creation time. This order is reflected when iterating over the sorted map's collection views (returned by the entrySet, keySet and values methods). Several additional operations are provided to take advantage of the ordering. (This interface is the map analogue of the SortedSet interface.)

All keys inserted into a sorted map must implement the Comparable interface (or be accepted by the specified comparator). Furthermore, all such keys must be mutually comparable: k1.compareTo(k2) (or comparator.compare(k1, k2)) must not throw a ClassCastException for any elements k1 and k2 in the sorted map. Attempts to violate this restriction will cause the offending method or constructor invocation to throw a ClassCastException.

Note that the ordering maintained by a sorted map (whether or not an explicit comparator is provided) must be consistent with equals if the sorted map is to correctly implement the Map interface. (See the Comparable interface or Comparator interface for a precise definition of consistent with equals.) This is so because the Map interface is defined in terms of the equals operation, but a sorted map performs all key comparisons using its compareTo (or 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 is well-defined even if its ordering is inconsistent with equals; it just fails to obey the general contract of the Map interface.

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 order of its keys. 2) A constructor with a single argument of type Comparator, which creates an empty sorted map sorted according to the specified comparator. 3) A constructor with a single argument of type Map, 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 sorted map, 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) but the JDK implementation (TreeMap) complies.

This interface is a member of the Java Collections Framework.

Since:
1.2
See Also:
Map sample code for java.util.Map definition code for java.util.Map , TreeMap sample code for java.util.TreeMap definition code for java.util.TreeMap , SortedSet sample code for java.util.SortedSet definition code for java.util.SortedSet , Comparator sample code for java.util.Comparator definition code for java.util.Comparator , Comparable sample code for java.lang.Comparable definition code for java.lang.Comparable , Collection sample code for java.util.Collection definition code for java.util.Collection , ClassCastException sample code for java.lang.ClassCastException definition code for java.lang.ClassCastException

Nested Class Summary
 
Nested classes/interfaces inherited from interface java.util.Map sample code for java.util.Map definition code for java.util.Map
Map.Entry sample code for java.util.Map.Entry definition code for java.util.Map.Entry <K,V>
 
Method Summary
 Comparator sample code for java.util.Comparator definition code for java.util.Comparator <? super K> comparator sample code for java.util.SortedMap.comparator() definition code for java.util.SortedMap.comparator() ()
          Returns the comparator associated with this sorted map, or null if it uses its keys' natural ordering.
 K firstKey sample code for java.util.SortedMap.firstKey() definition code for java.util.SortedMap.firstKey() ()
          Returns the first (lowest) key currently in this sorted map.
 SortedMap sample code for java.util.SortedMap definition code for java.util.SortedMap <K,V> headMap sample code for java.util.SortedMap.headMap(K) definition code for java.util.SortedMap.headMap(K) (K toKey)
          Returns a view of the portion of this sorted map whose keys are strictly less than toKey.
 K lastKey sample code for java.util.SortedMap.lastKey() definition code for java.util.SortedMap.lastKey() ()
          Returns the last (highest) key currently in this sorted map.
 SortedMap sample code for java.util.SortedMap definition code for java.util.SortedMap <K,V> subMap sample code for java.util.SortedMap.subMap(K, K) definition code for java.util.SortedMap.subMap(K, K) (K fromKey, K toKey)
          Returns a view of the portion of this sorted map whose keys range from fromKey, inclusive, to toKey, exclusive.
 SortedMap sample code for java.util.SortedMap definition code for java.util.SortedMap <K,V> tailMap sample code for java.util.SortedMap.tailMap(K) definition code for java.util.SortedMap.tailMap(K) (K fromKey)
          Returns a view of the portion of this sorted map whose keys are greater than or equal to fromKey.
 
Methods inherited from interface java.util.Map sample code for java.util.Map definition code for java.util.Map
clear sample code for java.util.Map.clear() definition code for java.util.Map.clear() , containsKey sample code for java.util.Map.containsKey(java.lang.Object) definition code for java.util.Map.containsKey(java.lang.Object) , containsValue sample code for java.util.Map.containsValue(java.lang.Object) definition code for java.util.Map.containsValue(java.lang.Object) , entrySet sample code for java.util.Map.entrySet() definition code for java.util.Map.entrySet() , equals sample code for java.util.Map.equals(java.lang.Object) definition code for java.util.Map.equals(java.lang.Object) , get sample code for java.util.Map.get(java.lang.Object) definition code for java.util.Map.get(java.lang.Object) , hashCode sample code for java.util.Map.hashCode() definition code for java.util.Map.hashCode() , isEmpty sample code for java.util.Map.isEmpty() definition code for java.util.Map.isEmpty() , keySet sample code for java.util.Map.keySet() definition code for java.util.Map.keySet() , put sample code for java.util.Map.put(K, V) definition code for java.util.Map.put(K, V) , putAll sample code for java.util.Map.putAll(java.util.Map) definition code for java.util.Map.putAll(java.util.Map) , remove sample code for java.util.Map.remove(java.lang.Object) definition code for java.util.Map.remove(java.lang.Object) , size sample code for java.util.Map.size() definition code for java.util.Map.size() , values sample code for java.util.Map.values() definition code for java.util.Map.values()
 

Method Detail

comparator sample code for java.util.SortedMap.comparator() definition code for java.util.SortedMap.comparator()

Comparator sample code for java.util.Comparator definition code for java.util.Comparator <? super K> comparator()
Returns the comparator associated with this sorted map, or null if it uses its keys' natural ordering.

Returns:
the comparator associated with this sorted map, or null if it uses its keys' natural ordering.

subMap sample code for java.util.SortedMap.subMap(K, K) definition code for java.util.SortedMap.subMap(K, K)

SortedMap sample code for java.util.SortedMap definition code for java.util.SortedMap <K,V> subMap(K fromKey,
                      K toKey)
Returns a view of the portion of this sorted map whose keys range from fromKey, inclusive, to toKey, exclusive. (If fromKey and toKey are equal, the returned sorted map is empty.) The returned sorted map is backed by this sorted map, so changes in the returned sorted map are reflected in this sorted map, and vice-versa. The returned Map supports all optional map operations that this sorted map supports.

The map returned by this method will throw an IllegalArgumentException if the user attempts to insert a key outside the specified range.

Note: this method always returns a half-open range (which includes its low endpoint but not its high endpoint). If you need a closed range (which includes both endpoints), and the key type allows for calculation of the successor a given key, merely request the subrange from lowEndpoint to successor(highEndpoint). For example, suppose that m is a map whose keys are strings. The following idiom obtains a view containing all of the key-value mappings in m whose keys are between low and high, inclusive:

    Map sub = m.subMap(low, high+"\0");
A similarly technique can be used to generate an open range (which contains neither endpoint). The following idiom obtains a view containing all of the key-value mappings in m whose keys are between low and high, exclusive:
    Map sub = m.subMap(low+"\0", high);

Parameters:
fromKey - low endpoint (inclusive) of the subMap.
toKey - high endpoint (exclusive) of the subMap.
Returns:
a view of the specified range within this sorted map.
Throws:
ClassCastException sample code for java.lang.ClassCastException definition code for java.lang.ClassCastException - if fromKey and 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 fromKey or toKey cannot be compared to keys currently in the map.
IllegalArgumentException sample code for java.lang.IllegalArgumentException definition code for java.lang.IllegalArgumentException - if fromKey is greater than toKey; or if this map is itself a subMap, headMap, or tailMap, and fromKey or toKey are not within the specified range of the subMap, headMap, or tailMap.
NullPointerException sample code for java.lang.NullPointerException definition code for java.lang.NullPointerException - if fromKey or toKey is null and this sorted map does not tolerate null keys.

headMap sample code for java.util.SortedMap.headMap(K) definition code for java.util.SortedMap.headMap(K)

SortedMap sample code for java.util.SortedMap definition code for java.util.SortedMap <K,V> headMap(K toKey)
Returns a view of the portion of this sorted map whose keys are strictly less than toKey. The returned sorted map is backed by this sorted map, so changes in the returned sorted map are reflected in this sorted map, and vice-versa. The returned map supports all optional map operations that this sorted map supports.

The map returned by this method will throw an IllegalArgumentException if the user attempts to insert a key outside the specified range.

Note: this method always returns a view that does not contain its (high) endpoint. If you need a view that does contain this endpoint, and the key type allows for calculation of the successor a given key, merely request a headMap bounded by successor(highEndpoint). For example, suppose that suppose that m is a map whose keys are strings. The following idiom obtains a view containing all of the key-value mappings in m whose keys are less than or equal to high:

    Map head = m.headMap(high+"\0");

Parameters:
toKey - high endpoint (exclusive) of the subMap.
Returns:
a view of the specified initial range of this sorted map.
Throws:
ClassCastException sample code for java.lang.ClassCastException definition code for java.lang.ClassCastException - if toKey is not compatible with this map's comparator (or, if the map has no comparator, if toKey does not implement Comparable). Implementations may, but are not required to, throw this exception if toKey cannot be compared to keys currently in the map.
IllegalArgumentException sample code for java.lang.IllegalArgumentException definition code for java.lang.IllegalArgumentException - if this map is itself a subMap, headMap, or tailMap, and toKey is not within the specified range of the subMap, headMap, or tailMap.
NullPointerException sample code for java.lang.NullPointerException definition code for java.lang.NullPointerException - if toKey is null and this sorted map does not tolerate null keys.

tailMap sample code for java.util.SortedMap.tailMap(K) definition code for java.util.SortedMap.tailMap(K)

SortedMap sample code for java.util.SortedMap definition code for java.util.SortedMap <K,V> tailMap(K fromKey)
Returns a view of the portion of this sorted map whose keys are greater than or equal to fromKey. The returned sorted map is backed by this sorted map, so changes in the returned sorted map are reflected in this sorted map, and vice-versa. The returned map supports all optional map operations that this sorted map supports.

The map returned by this method will throw an IllegalArgumentException if the user attempts to insert a key outside the specified range.

Note: this method always returns a view that contains its (low) endpoint. If you need a view that does not contain this endpoint, and the element type allows for calculation of the successor a given value, merely request a tailMap bounded by successor(lowEndpoint). For example, suppose that suppose that m is a map whose keys are strings. The following idiom obtains a view containing all of the key-value mappings in m whose keys are strictly greater than low:

    Map tail = m.tailMap(low+"\0");

Parameters:
fromKey - low endpoint (inclusive) of the tailMap.
Returns:
a view of the specified final range of this sorted map.
Throws:
ClassCastException sample code for java.lang.ClassCastException definition code for java.lang.ClassCastException - if fromKey is not compatible with this map's comparator (or, if the map has no comparator, if fromKey does not implement Comparable). Implementations may, but are not required to, throw this exception if fromKey cannot be compared to keys currently in the map.
IllegalArgumentException sample code for java.lang.IllegalArgumentException definition code for java.lang.IllegalArgumentException - if this map is itself a subMap, headMap, or tailMap, and fromKey is not within the specified range of the subMap, headMap, or tailMap.
NullPointerException sample code for java.lang.NullPointerException definition code for java.lang.NullPointerException - if fromKey is null and this sorted map does not tolerate null keys.

firstKey sample code for java.util.SortedMap.firstKey() definition code for java.util.SortedMap.firstKey()

K firstKey()
Returns the first (lowest) key currently in this sorted map.

Returns:
the first (lowest) key currently in this sorted map.
Throws:
NoSuchElementException sample code for java.util.NoSuchElementException definition code for java.util.NoSuchElementException - if this map is empty.

lastKey sample code for java.util.SortedMap.lastKey() definition code for java.util.SortedMap.lastKey()

K lastKey()
Returns the last (highest) key currently in this sorted map.

Returns:
the last (highest) key currently in this sorted map.
Throws:
NoSuchElementException sample code for java.util.NoSuchElementException definition code for java.util.NoSuchElementException - if this map is empty.