org.apache.commons.collections.map

Class CompositeMap

Implemented Interfaces:
Map

public class CompositeMap
extends java.lang.Object
implements Map

Decorates a map of other maps to provide a single unified view.

Changes made to this map will actually be made on the decorated map. Add and remove operations require the use of a pluggable strategy. If no strategy is provided then add and remove are unsupported.

Version:
$Revision: 1.7 $ $Date: 2004/02/18 01:13:19 $
Author:
Brian McCallister
Since:
Commons Collections 3.0

Nested Class Summary

static interface
CompositeMap.MapMutator
This interface allows definition for all of the indeterminate mutators in a CompositeMap, as well as providing a hook for callbacks on key collisions.

Constructor Summary

CompositeMap()
Create a new, empty, CompositeMap.
CompositeMap(Map one, Map two)
Create a new CompositeMap with two composited Map instances.
CompositeMap(Map one, Map two, CompositeMap.MapMutator mutator)
Create a new CompositeMap with two composited Map instances.
CompositeMap(Map[] composite)
Create a new CompositeMap which composites all of the Map instances in the argument.
CompositeMap(Map[] composite, CompositeMap.MapMutator mutator)
Create a new CompositeMap which composites all of the Map instances in the argument.

Method Summary

void
addComposited(Map map)
Add an additional Map to the composite.
void
clear()
Calls clear() on all composited Maps.
boolean
containsKey(Object key)
Returns true if this map contains a mapping for the specified key.
boolean
containsValue(Object value)
Returns true if this map maps one or more keys to the specified value.
Set
entrySet()
Returns a set view of the mappings contained in this map.
boolean
equals(Object obj)
Checks if this Map equals another as per the Map specification.
Object
get(Object key)
Returns the value to which this map maps the specified key.
int
hashCode()
Gets a hash code for the Map as per the Map specification.
boolean
isEmpty()
Returns true if this map contains no key-value mappings.
Set
keySet()
Returns a set view of the keys contained in this map.
Object
put(Object key, Object value)
Associates the specified value with the specified key in this map (optional operation).
void
putAll(Map map)
Copies all of the mappings from the specified map to this map (optional operation).
Object
remove(Object key)
Removes the mapping for this key from this map if it is present (optional operation).
Map
removeComposited(Map map)
Remove a Map from the composite.
void
setMutator(CompositeMap.MapMutator mutator)
Specify the MapMutator to be used by mutation operations.
int
size()
Returns the number of key-value mappings in this map.
Collection
values()
Returns a collection view of the values contained in this map.

Constructor Details

CompositeMap

public CompositeMap()
Create a new, empty, CompositeMap.

CompositeMap

public CompositeMap(Map one,
                    Map two)
Create a new CompositeMap with two composited Map instances.
Parameters:
one - the first Map to be composited
two - the second Map to be composited

CompositeMap

public CompositeMap(Map one,
                    Map two,
                    CompositeMap.MapMutator mutator)
Create a new CompositeMap with two composited Map instances.
Parameters:
one - the first Map to be composited
two - the second Map to be composited
mutator - MapMutator to be used for mutation operations

CompositeMap

public CompositeMap(Map[] composite)
Create a new CompositeMap which composites all of the Map instances in the argument. It copies the argument array, it does not use it directly.
Parameters:
composite - the Maps to be composited

CompositeMap

public CompositeMap(Map[] composite,
                    CompositeMap.MapMutator mutator)
Create a new CompositeMap which composites all of the Map instances in the argument. It copies the argument array, it does not use it directly.
Parameters:
composite - Maps to be composited
mutator - MapMutator to be used for mutation operations

Method Details

addComposited

public void addComposited(Map map)
            throws IllegalArgumentException
Add an additional Map to the composite.
Parameters:
map - the Map to be added to the composite

clear

public void clear()
Calls clear() on all composited Maps.

containsKey

public boolean containsKey(Object key)
Returns true if this map contains a mapping for the specified key. More formally, returns true if and only if this map contains at a mapping for a key k such that (key==null ? k==null : key.equals(k)). (There can be at most one such mapping.)
Parameters:
key - key whose presence in this map is to be tested.
Returns:
true if this map contains a mapping for the specified key.

containsValue

public boolean containsValue(Object value)
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.
Parameters:
value - value whose presence in this map is to be tested.
Returns:
true if this map maps one or more keys to the specified value.

entrySet

public Set entrySet()
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, 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.

This implementation returns a CompositeSet which composites the entry sets from all of the composited maps.

Returns:
a set view of the mappings contained in this map.

equals

public boolean equals(Object obj)
Checks if this Map equals another as per the Map specification.
Parameters:
obj - the object to compare to
Returns:
true if the maps are equal

get

public Object get(Object key)
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.)

Parameters:
key - key whose associated value is to be returned.
Returns:
the value to which this map maps the specified key, or null if the map contains no mapping for this key.

hashCode

public int hashCode()
Gets a hash code for the Map as per the Map specification.

isEmpty

public boolean isEmpty()
Returns true if this map contains no key-value mappings.
Returns:
true if this map contains no key-value mappings.

keySet

public Set keySet()
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, 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.

This implementation returns a CompositeSet which composites the key sets from all of the composited maps.

Returns:
a set view of the keys contained in this map.

put

public Object put(Object key,
                  Object value)
Parameters:
key - key with which the specified value is to be associated.
value - value to be associated with the specified key.
Returns:
previous value associated with specified key, or null if there was no mapping for key. A null return can also indicate that the map previously associated null with the specified key, if the implementation supports null values.

putAll

public void putAll(Map map)
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.
Parameters:
map - Mappings to be stored in this map.

remove

public Object remove(Object key)
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.

Parameters:
key - key whose mapping is to be removed from the map.
Returns:
previous value associated with specified key, or null if there was no mapping for key.

removeComposited

public Map removeComposited(Map map)
Remove a Map from the composite.
Parameters:
map - the Map to be removed from the composite
Returns:
The removed Map or null if map is not in the composite

setMutator

public void setMutator(CompositeMap.MapMutator mutator)
Specify the MapMutator to be used by mutation operations.
Parameters:
mutator - the MapMutator to be used for mutation delegation

size

public int size()
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:
the number of key-value mappings in this map.

values

public Collection values()
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, 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.
Returns:
a collection view of the values contained in this map.

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