Interface SortedMap<K,V>
- Type Parameters:
-
K
- the type of keys maintained by this map -
V
- the type of mapped values
- All Superinterfaces:
Map<K,V>
- All Known Subinterfaces:
-
ConcurrentNavigableMap<K,V>
,NavigableMap<K,V>
- All Known Implementing Classes:
-
ConcurrentSkipListMap
,TreeMap
public interface SortedMap<K,V> extends Map<K,V>
A Map
that further provides a total ordering on its keys. The map is ordered according to the natural ordering of its keys, or by a Comparator
typically 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 SortedSet
.)
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 keys 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. 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:
- A void (no arguments) constructor, which creates an empty sorted map sorted according to the natural ordering of its keys.
- A constructor with a single argument of type
Comparator
, which creates an empty sorted map sorted according to the specified comparator. - 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. - A constructor with a single argument of type
SortedMap
, which creates a new sorted map with the same key-value mappings and the same ordering as the input sorted map.
Note: several methods return submaps with restricted key ranges. Such ranges are half-open, that is, they include their low endpoint but not their high endpoint (where applicable). If you need a closed range (which includes both endpoints), and the key type allows for calculation of the successor of 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:
SortedMap<String, V> sub = m.subMap(low, high+"\0");A similar 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:SortedMap<String, V> sub = m.subMap(low+"\0", high);
This interface is a member of the Java Collections Framework.
- Since:
- 1.2
- See Also:
-
Map
,TreeMap
,SortedSet
,Comparator
,Comparable
,Collection
,ClassCastException
Nested Class Summary
Nested classes/interfaces declared in interface java.util.Map
Map.Entry<K,V>
Method Summary
Modifier and Type | Method | Description |
---|---|---|
Comparator<? super K> | comparator() | Returns the comparator used to order the keys in this map, or |
Set<Map.Entry<K,V>> | entrySet() | Returns a |
K | firstKey() | Returns the first (lowest) key currently in this map. |
SortedMap<K,V> | headMap(K toKey) | Returns a view of the portion of this map whose keys are strictly less than |
Set<K> | keySet() | Returns a |
K | lastKey() | Returns the last (highest) key currently in this map. |
SortedMap<K,V> | subMap(K fromKey,
K toKey) | Returns a view of the portion of this map whose keys range from |
SortedMap<K,V> | tailMap(K fromKey) | Returns a view of the portion of this map whose keys are greater than or equal to |
Collection<V> | values() | Returns a |
Methods declared in interface java.util.Map
clear, compute, computeIfAbsent, computeIfPresent, containsKey, containsValue, equals, forEach, get, getOrDefault, hashCode, isEmpty, merge, put, putAll, putIfAbsent, remove, remove, replace, replace, replaceAll, size
Method Detail
comparator
Comparator<? super K> comparator()
Returns the comparator used to order the keys in this map, or null
if this map uses the natural ordering of its keys.
- Returns:
- the comparator used to order the keys in this map, or
null
if this map uses the natural ordering of its keys
subMap
SortedMap<K,V> subMap(K fromKey, K toKey)
Returns a view of the portion of this map whose keys range from fromKey
, inclusive, to toKey
, exclusive. (If fromKey
and 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.
The returned map will throw an IllegalArgumentException
on an attempt to insert a key outside its range.
- Parameters:
-
fromKey
- low endpoint (inclusive) of the keys in the returned map -
toKey
- high endpoint (exclusive) of the keys in the returned map - Returns:
- a view of the portion of this map whose keys range from
fromKey
, inclusive, totoKey
, exclusive - Throws:
-
ClassCastException
- iffromKey
andtoKey
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 iffromKey
ortoKey
cannot be compared to keys currently in the map. -
NullPointerException
- iffromKey
ortoKey
is null and this map does not permit null keys -
IllegalArgumentException
- iffromKey
is greater thantoKey
; or if this map itself has a restricted range, andfromKey
ortoKey
lies outside the bounds of the range
headMap
SortedMap<K,V> headMap(K toKey)
Returns a view of the portion of this map whose keys are strictly less than 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.
The returned map will throw an IllegalArgumentException
on an attempt to insert a key outside its range.
- Parameters:
-
toKey
- high endpoint (exclusive) of the keys in the returned map - Returns:
- a view of the portion of this map whose keys are strictly less than
toKey
- Throws:
-
ClassCastException
- iftoKey
is not compatible with this map's comparator (or, if the map has no comparator, iftoKey
does not implementComparable
). Implementations may, but are not required to, throw this exception iftoKey
cannot be compared to keys currently in the map. -
NullPointerException
- iftoKey
is null and this map does not permit null keys -
IllegalArgumentException
- if this map itself has a restricted range, andtoKey
lies outside the bounds of the range
tailMap
SortedMap<K,V> tailMap(K fromKey)
Returns a view of the portion of this map whose keys are greater than or equal to 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.
The returned map will throw an IllegalArgumentException
on an attempt to insert a key outside its range.
- Parameters:
-
fromKey
- low endpoint (inclusive) of the keys in the returned map - Returns:
- a view of the portion of this map whose keys are greater than or equal to
fromKey
- Throws:
-
ClassCastException
- iffromKey
is not compatible with this map's comparator (or, if the map has no comparator, iffromKey
does not implementComparable
). Implementations may, but are not required to, throw this exception iffromKey
cannot be compared to keys currently in the map. -
NullPointerException
- iffromKey
is null and this map does not permit null keys -
IllegalArgumentException
- if this map itself has a restricted range, andfromKey
lies outside the bounds of the range
firstKey
K firstKey()
Returns the first (lowest) key currently in this map.
- Returns:
- the first (lowest) key currently in this map
- Throws:
-
NoSuchElementException
- if this map is empty
lastKey
K lastKey()
Returns the last (highest) key currently in this map.
- Returns:
- the last (highest) key currently in this map
- Throws:
-
NoSuchElementException
- if this map is empty
keySet
Set<K> keySet()
Returns a 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 remove
operation), the results of the iteration are undefined. The set supports element removal, which removes the corresponding mapping from the map, via the Iterator.remove
, Set.remove
, removeAll
, retainAll
, and clear
operations. It does not support the add
or addAll
operations.
- Specified by:
-
keySet
in interfaceMap<K,V>
- Returns:
- a set view of the keys contained in this map, sorted in ascending order
values
Collection<V> values()
Returns a 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 remove
operation), the results of the iteration are undefined. The collection supports element removal, which removes the corresponding mapping from the map, via the Iterator.remove
, Collection.remove
, removeAll
, retainAll
and clear
operations. It does not support the add
or addAll
operations.
- Specified by:
-
values
in interfaceMap<K,V>
- Returns:
- a collection view of the values contained in this map, sorted in ascending key order
entrySet
Set<Map.Entry<K,V>> entrySet()
Returns a 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 remove
operation, or through the 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 Iterator.remove
, Set.remove
, removeAll
, retainAll
and clear
operations. It does not support the add
or addAll
operations.