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.
Removes all mappings from this map (optional operation).
Returns the comparator associated with this sorted map, or
null if it uses its keys' natural ordering.
Returns true if this map contains a mapping for the specified
key. More formally, returns true if and only if
this map contains a mapping for a key k such that
(key==null ? k==null : key.equals(k)). (There can be
at most one such mapping.)
Returns true if this map maps one or more keys to the
specified value. More formally, returns true if and only if
this map contains at least one mapping to a value v such that
(value==null ? v==null : value.equals(v)). This operation
will probably require time linear in the map size for most
implementations of the Map interface.
Returns a set view of the mappings contained in this map. Each element
in the returned set is a
Map.Entry
. 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.
Compares the specified object with this map for equality. Returns
true if the given object is also a map and the two Maps
represent the same mappings. More formally, two maps t1 and
t2 represent the same mappings if
t1.entrySet().equals(t2.entrySet()). This ensures that the
equals method works properly across different implementations
of the Map interface.
Returns the first (lowest) key currently in this sorted map.
Returns the value to which this map maps the specified key. Returns
null if the map contains no mapping for this key. A return
value of
null does not
necessarily indicate that the
map contains no mapping for the key; it's also possible that the map
explicitly maps the key to
null. The
containsKey
operation may be used to distinguish these two cases.
More formally, if this map contains a mapping from a key
k to a value v such that (key==null ? k==null :
key.equals(k)), then this method returns v; otherwise
it returns null. (There can be at most one such mapping.)
Returns the hash code value for this map. The hash code of a map
is defined to be the sum of the hashCodes of each entry in the map's
entrySet view. This ensures that t1.equals(t2) implies
that t1.hashCode()==t2.hashCode() for any two maps
t1 and t2, as required by the general
contract of Object.hashCode.
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");
Returns true if this map contains no key-value mappings.
Returns a set view of the keys contained in this map. 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.
Returns the last (highest) key currently in this sorted map.
Associates the specified value with the specified key in this map
(optional operation). If the map previously contained a mapping for
this key, the old value is replaced by the specified value. (A map
m is said to contain a mapping for a key
k if and only
if
m.containsKey(k)
would return
true.))
Copies all of the mappings from the specified map to this map
(optional operation). The effect of this call is equivalent to that
of calling
put(k, v)
on this map once
for each mapping from key
k to value
v in the
specified map. The behavior of this operation is unspecified if the
specified map is modified while the operation is in progress.
Removes the mapping for this key from this map if it is present
(optional operation). More formally, if this map contains a mapping
from key
k to value
v such that
(key==null ? k==null : key.equals(k)), that mapping
is removed. (The map can contain at most one such mapping.)
Returns the value to which the map previously associated the key, or
null if the map contained no mapping for this key. (A
null return can also indicate that the map previously
associated null with the specified key if the implementation
supports null values.) The map will not contain a mapping for
the specified key once the call returns.
Returns the number of key-value mappings in this map. If the
map contains more than Integer.MAX_VALUE elements, returns
Integer.MAX_VALUE.
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);
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");
Returns a collection view of the values contained in this map. 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.