java::util::SortedMap Class Reference

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java::util::TreeMapjava::util::Mapjava::lang::Interfacejava::lang::Object
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Collaboration diagram for java::util::SortedMap:

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java::util::Mapjava::lang::Interfacejava::lang::Object
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List of all members.


Detailed Description

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 SDK implementation (TreeMap) complies.

Author:
Josh Bloch
Version:
1.13, 12/03/01
See also:
Map

TreeMap

SortedSet

Comparator

Comparable

Collection

ClassCastException

Since:
1.2

Public Member Functions

virtual Ref< Comparatorcomparator () const =0
 Returns the comparator associated with this sorted map, or null if it uses its keys' natural ordering.
virtual Ref< SortedMapsubMap (const ObjectRef &fromKey, const ObjectRef &toKey) const =0
 Returns a view of the portion of this sorted map whose keys range from fromKey, inclusive, to toKey, exclusive.
virtual Ref< SortedMapheadMap (const ObjectRef &toKey) const =0
 Returns a view of the portion of this sorted map whose keys are strictly less than toKey.
virtual Ref< SortedMaptailMap (const ObjectRef &fromKey) const =0
 Returns a view of the portion of this sorted map whose keys are greater than or equal to fromKey.
virtual ObjectRef firstKey () const =0
 Returns the first (lowest) key currently in this sorted map.
virtual ObjectRef lastKey () const =0
 Returns the last (highest) key currently in this sorted map.

Static Public Member Functions

static Ref< SortedMapsynchronizedSortedMap (const Ref< SortedMap > &map, const Ref< Sync > &sync=0)
 Returns a synchronized (thread-safe) sorted map backed by the specified sorted map.
static Ref< SortedMapimmutableSortedMap (const Ref< SortedMap > &map)
 Returns an unmodifiable view of the specified sorted map.

Member Function Documentation

static Ref<SortedMap> java::util::SortedMap::synchronizedSortedMap ( const Ref< SortedMap > &  map,
const Ref< Sync > &  sync = 0 
) [static]

Returns a synchronized (thread-safe) sorted map backed by the specified sorted map.

In order to guarantee serial access, it is critical that all access to the backing sorted map is accomplished through the returned sorted map (or its views).

It is imperative that the user manually synchronize on the returned sorted map when iterating over any of its collection views, or the collections views of any of its subMap, headMap or tailMap views.

  SortedMap m = Collections.synchronizedSortedMap(new HashSortedMap());
      ...
  Set s = m.keySet();  // Needn't be in synchronized block
      ...
  synchronized(m) {  // Synchronizing on m, not s!
      Iterator i = s.iterator(); // Must be in synchronized block
      while (i.hasNext())
          foo(i.next());
  }
 
or:
  SortedMap m = Collections.synchronizedSortedMap(new HashSortedMap());
  SortedMap m2 = m.subMap(foo, bar);
      ...
  Set s2 = m2.keySet();  // Needn't be in synchronized block
      ...
  synchronized(m) {  // Synchronizing on m, not m2 or s2!
      Iterator i = s.iterator(); // Must be in synchronized block
      while (i.hasNext())
          foo(i.next());
  }
 
Failure to follow this advice may result in non-deterministic behavior.

The returned sorted map will be serializable if the specified sorted map is serializable.

Parameters:
m the sorted map to be "wrapped" in a synchronized sorted map.
Returns:
a synchronized view of the specified sorted map.

static Ref<SortedMap> java::util::SortedMap::immutableSortedMap ( const Ref< SortedMap > &  map  )  [static]

Returns an unmodifiable view of the specified sorted map.

This method allows modules to provide users with "read-only" access to internal sorted maps. Query operations on the returned sorted map "read through" to the specified sorted map. Attempts to modify the returned sorted map, whether direct, via its collection views, or via its subMap, headMap, or tailMap views, result in an UnsupportedOperationException.

The returned sorted map will be serializable if the specified sorted map is serializable.

Parameters:
m the sorted map for which an unmodifiable view is to be returned.
Returns:
an unmodifiable view of the specified sorted map.

virtual Ref<Comparator> java::util::SortedMap::comparator (  )  const [pure virtual]

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.

Implemented in java::util::TreeMap.

virtual Ref<SortedMap> java::util::SortedMap::subMap ( const ObjectRef fromKey,
const ObjectRef toKey 
) const [pure virtual]

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+"");

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+"", 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.
Exceptions:
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 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 if fromKey or toKey is null and this sorted map does not tolerate null keys.

Implemented in java::util::TreeMap.

virtual Ref<SortedMap> java::util::SortedMap::headMap ( const ObjectRef toKey  )  const [pure virtual]

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+"");

Parameters:
toKey high endpoint (exclusive) of the subMap.
Returns:
a view of the specified initial range of this sorted map.
Exceptions:
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 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 if toKey is null and this sorted map does not tolerate null keys.

Implemented in java::util::TreeMap.

virtual Ref<SortedMap> java::util::SortedMap::tailMap ( const ObjectRef fromKey  )  const [pure virtual]

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+"");

Parameters:
fromKey low endpoint (inclusive) of the tailMap.
Returns:
a view of the specified final range of this sorted map.
Exceptions:
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 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 if fromKey is null and this sorted map does not tolerate null keys.

Implemented in java::util::TreeMap.

virtual ObjectRef java::util::SortedMap::firstKey (  )  const [pure virtual]

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

Returns:
the first (lowest) key currently in this sorted map.
Exceptions:
NoSuchElementException if this map is empty.

Implemented in java::util::TreeMap.

virtual ObjectRef java::util::SortedMap::lastKey (  )  const [pure virtual]

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

Returns:
the last (highest) key currently in this sorted map.
Exceptions:
NoSuchElementException if this map is empty.

Implemented in java::util::TreeMap.


The documentation for this class was generated from the following file:
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