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java.util
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:
Implementing Classes:
-
ConcurrentNavigableMap
TreeMap
<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
A map that further guarantees that it will be in ascending key order, sorted according to the
total
natural
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
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
SortedSet
.)
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
keys
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 ordering 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
SortedMap
, 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.
Note: several methods return submaps with restricted key ranges. Such ranges are
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
half-open
natural order
, 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
of its keys. 2) A constructor with a single argument of type
lowEndpoint
Comparator
to
, which creates an empty sorted map sorted according to the specified comparator. 3) A constructor with a single argument of type
successor(highEndpoint)
Map
. 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);
, 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
,
TreeMap
,
SortedSet
,
Comparator
,
Comparable
,
Collection
,
ClassCastException
Nested classes/interfaces inherited from interface java.util.
Map
|
Map.Entry
<
K
,
V
> |
Method Summary
|
Comparator
<? super
K
|
comparator
()
Returns the comparator
used to order the keys in
associated with
this
sorted
map, or
null
if
this map
it
uses
the
natural ordering
its keys' natural ordering.
|
Set
<
Map.Entry
<
K
,
V
|
entrySet
firstKey
()
Returns
a
Set
the first (lowest) key currently in this sorted map.
|
K
|
firstKey
()
Returns the first (lowest) key currently in this map.
|
SortedMap
<
K
,
V
|
headMap
(
K
Returns a view of the portion of this sorted map whose keys are strictly less than toKey.
|
SortedMap
<
K
,
V
|
headMap
(
K
Returns a view of the portion of this map whose keys are strictly less than
toKey
.
|
K
|
lastKey
()
Returns the last (highest) key currently in this sorted map.
|
Set
<
K
|
keySet
()
Returns a
Set
|
SortedMap
<
K
,
V
|
subMap
(
K
fromKey,
K
Returns a view of the portion of this sorted map whose keys range from
fromKey
, inclusive, to
toKey
, exclusive.
|
K
|
lastKey
()
Returns the last (highest) key currently in this map.
|
SortedMap
<
K
,
V
|
tailMap
(
K
Returns a view of the portion of this sorted map whose keys are greater than or equal to
fromKey
.
|
SortedMap
<
K
,
V
|
subMap
(
K
fromKey,
K
Returns a view of the portion of this map whose keys range from
fromKey
, inclusive, to
toKey
, exclusive.
|
SortedMap
<
K
,
V
|
tailMap
(
K
Returns a view of the portion of this map whose keys are greater than or equal to
fromKey
.
|
Collection
<
V
|
values
()
Returns a
Collection
|
Methods inherited from interface java.util.
Map
|
clear
,
containsKey
,
containsValue
,
entrySet
,
equals
,
get
,
hashCode
,
isEmpty
,
keySet
,
put
,
putAll
,
remove
,
size
,
values
|
comparator
Comparator<? super K> comparator()
-
Returns the comparator
used to order the keys in
associated with
this
sorted
map, or
null
if this map uses the
natural ordering
of its keys.
if it uses its keys' natural ordering.
-
-
-
Returns:
-
the comparator
used to order the keys in
associated with
this
sorted
map, or
null
if this map uses the natural ordering of its keys
if it uses its keys' natural ordering.
subMap
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
Map
supports all optional map operations that this
sorted
map supports.
The
map
returned
map
by this method
will throw an
IllegalArgumentException
on an attempt
if the user attempts
to insert a key outside
its
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:
![](../../diffpics/oold.gif)
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:
![](../../diffpics/oold.gif)
Map sub = m.subMap(low+"\0", high);
-
-
-
Parameters:
-
fromKey - low endpoint (inclusive) of the
keys in the returned map
subMap.
-
toKey - high endpoint (exclusive) of the
keys in the returned map
subMap.
-
Returns:
-
a view of the portion of this map whose keys range from
fromKey
, inclusive, to
toKey
, exclusive
a view of the specified range within this sorted map.
-
Throws:
-
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.
-
NullPointerException
IllegalArgumentException
- if
fromKey
is greater than
toKey
; or if this map is itself a subMap, headMap, or tailMap, and
fromKey
or
toKey
is null and this map does not permit null keys
are not within the specified range of the subMap, headMap, or tailMap.
-
IllegalArgumentException
NullPointerException
- if
fromKey
is greater than
or
toKey
; or if this map itself has a restricted range, and
is
fromKey
null
or
and this sorted map does not tolerate
toKey
null
lies outside the bounds of the range
keys.
headMap
SortedMap<K,V> headMap(K toKey)
-
Returns a view of the portion of this map whose keys are strictly less than
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
toKey
m
. 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
is a map whose keys are strings. The following idiom obtains a view containing all of the key-value mappings in
IllegalArgumentException
m
on an attempt to insert a key outside its range.
whose keys are less than or equal to
high
:
![](../../diffpics/oold.gif)
Map head = m.headMap(high+"\0");
-
-
-
Parameters:
-
toKey - high endpoint (exclusive) of the
keys in the returned map
subMap.
-
Returns:
-
a view of the portion of this map whose keys are strictly less than
toKey
a view of the specified initial range of this sorted map.
-
Throws:
-
ClassCastException
- if
toKey
is not compatible with this map's comparator (or, if the map has no comparator, if
toKey
does not implement
Comparable
Comparable
). Implementations may, but are not required to, throw this exception if
toKey
cannot be compared to keys currently in the map.-
NullPointerException
IllegalArgumentException
- if
- if this map is itself a subMap, headMap, or tailMap, and
toKey
is null and this map does not permit null keys
is not within the specified range of the subMap, headMap, or tailMap.
-
IllegalArgumentException
NullPointerException
- if this map itself has a restricted range, and
- if
toKey
lies outside the bounds of the range
is
null
and this sorted map does not tolerate
null
keys.
tailMap
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
map
by this method
will throw an
IllegalArgumentException
on an attempt
if the user attempts
to insert a key outside
its
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
:
![](../../diffpics/oold.gif)
Map tail = m.tailMap(low+"\0");
-
-
-
Parameters:
-
fromKey - low endpoint (inclusive) of the
keys in the returned map
tailMap.
-
Returns:
-
a view of the portion of this map whose keys are greater than or equal to
fromKey
a view of the specified final range of this sorted map.
-
Throws:
-
ClassCastException
- if
fromKey
is not compatible with this map's comparator (or, if the map has no comparator, if
fromKey
does not implement
Comparable
Comparable
). Implementations may, but are not required to, throw this exception if
fromKey
cannot be compared to keys currently in the map.-
NullPointerException
IllegalArgumentException
- if
- if this map is itself a subMap, headMap, or tailMap, and
fromKey
is null and this map does not permit null keys
is not within the specified range of the subMap, headMap, or tailMap.
-
IllegalArgumentException
NullPointerException
- if this map itself has a restricted range, and
- if
fromKey
lies outside the bounds of the range
is
null
and this sorted map does not tolerate
null
keys.
firstKey
K firstKey()
-
Returns the first (lowest) key currently in this
sorted
map.
-
-
-
Returns:
-
the first (lowest) key currently in this
map
sorted map.
-
Throws:
-
NoSuchElementException
- if this map is
empty
empty.
lastKey
K lastKey()
-
Returns the last (highest) key currently in this
sorted
map.
-
-
-
Returns:
-
the last (highest) key currently in this
map
sorted map.
-
Throws:
-
NoSuchElementException
- if this map is
empty
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 interface
Map
<
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 interface
Map
<
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.
-
-
Specified by:
-
entrySet
in interface
Map
<
K
,
V
>
-
-
Returns:
-
a set view of the mappings contained in this map, sorted in ascending key order