SortedMappublic interface SortedMap implements Map| A {@link Map} that further provides a total ordering on its keys.
The map is ordered according to the {@linkplain Comparable natural
ordering} of its keys, or by a {@link 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 {@link
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: 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 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. |
| Methods Summary |
|---|
| public java.util.Comparator | comparator()Returns the comparator used to order the keys in this map, or
null if this map uses the {@linkplain Comparable
natural ordering} of its keys.
| | public java.util.Set | entrySet()Returns a {@link 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.
| | public K | firstKey()Returns the first (lowest) key currently in this map.
| | public java.util.SortedMap | 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.
| | public java.util.Set | keySet()Returns a {@link 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.
| | public K | lastKey()Returns the last (highest) key currently in this map.
| | public java.util.SortedMap | 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.
| | public java.util.SortedMap | 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.
| | public java.util.Collection | values()Returns a {@link 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.
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