org.apache.commons.collections.map

Class CompositeMap

java.lang.Object

org.apache.commons.collections.map.CompositeMap

All Implemented Interfaces:

java.util.Map

public class CompositeMap
extends java.lang.Object
implements java.util.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.

Note that CompositeMap is not synchronized and is not thread-safe. If you wish to use this map from multiple threads concurrently, you must use appropriate synchronization. The simplest approach is to wrap this map using Collections.synchronizedMap(Map). This class may throw exceptions when accessed by concurrent threads without synchronization.

Since:

Commons Collections 3.0

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
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.

Nested classes/interfaces inherited from interface java.util.Map

java.util.Map.Entry<K,V>

Constructor Summary

Constructors

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

Method Summary

Modifier and Type	Method and Description
void	addComposited(java.util.Map map) Add an additional Map to the composite.
void	clear() Calls clear() on all composited Maps.
boolean	containsKey(java.lang.Object key) Returns true if this map contains a mapping for the specified key.
boolean	containsValue(java.lang.Object value) Returns true if this map maps one or more keys to the specified value.
java.util.Set	entrySet() Returns a set view of the mappings contained in this map.
boolean	equals(java.lang.Object obj) Checks if this Map equals another as per the Map specification.
java.lang.Object	get(java.lang.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.
java.util.Set	keySet() Returns a set view of the keys contained in this map.
java.lang.Object	put(java.lang.Object key, java.lang.Object value) Associates the specified value with the specified key in this map (optional operation).
void	putAll(java.util.Map map) Copies all of the mappings from the specified map to this map (optional operation).
java.lang.Object	remove(java.lang.Object key) Removes the mapping for this key from this map if it is present (optional operation).
java.util.Map	removeComposited(java.util.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.
java.util.Collection	values() Returns a collection view of the values contained in this map.

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface java.util.Map

compute, computeIfAbsent, computeIfPresent, forEach, getOrDefault, merge, putIfAbsent, remove, replace, replace, replaceAll

Constructor Detail

CompositeMap

public CompositeMap()

Create a new, empty, CompositeMap.

CompositeMap

public CompositeMap(java.util.Map one,
                    java.util.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

Throws:

java.lang.IllegalArgumentException - if there is a key collision

CompositeMap

public CompositeMap(java.util.Map one,
                    java.util.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(java.util.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

Throws:

java.lang.IllegalArgumentException - if there is a key collision

CompositeMap

public CompositeMap(java.util.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 Detail

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

addComposited

public void addComposited(java.util.Map map)
                   throws java.lang.IllegalArgumentException

Add an additional Map to the composite.

Parameters:

map - the Map to be added to the composite

Throws:

java.lang.IllegalArgumentException - if there is a key collision and there is no MapMutator set to handle it.

removeComposited

public java.util.Map removeComposited(java.util.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

clear

public void clear()

Calls clear() on all composited Maps.

Specified by:

clear in interface java.util.Map

Throws:

java.lang.UnsupportedOperationException - if any of the composited Maps do not support clear()

containsKey

public boolean containsKey(java.lang.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.)

Specified by:

containsKey in interface java.util.Map

Parameters:

key - key whose presence in this map is to be tested.

Returns:

true if this map contains a mapping for the specified key.

Throws:

java.lang.ClassCastException - if the key is of an inappropriate type for this map (optional).

java.lang.NullPointerException - if the key is null and this map does not not permit null keys (optional).

containsValue

public boolean containsValue(java.lang.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.

Specified by:

containsValue in interface java.util.Map

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.

Throws:

java.lang.ClassCastException - if the value is of an inappropriate type for this map (optional).

java.lang.NullPointerException - if the value is null and this map does not not permit null values (optional).

entrySet

public java.util.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.

Specified by:

entrySet in interface java.util.Map

Returns:

a set view of the mappings contained in this map.

See Also:

CompositeSet

get

public java.lang.Object get(java.lang.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.)

Specified by:

get in interface java.util.Map

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.

Throws:

java.lang.ClassCastException - if the key is of an inappropriate type for this map (optional).

java.lang.NullPointerException - key is null and this map does not not permit null keys (optional).

See Also:

containsKey(Object)

isEmpty

public boolean isEmpty()

Returns true if this map contains no key-value mappings.

Specified by:

isEmpty in interface java.util.Map

Returns:

true if this map contains no key-value mappings.

keySet

public java.util.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.

Specified by:

keySet in interface java.util.Map

Returns:

a set view of the keys contained in this map.

put

public java.lang.Object put(java.lang.Object key,
                            java.lang.Object value)

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.))

Specified by:

put in interface java.util.Map

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.

Throws:

java.lang.UnsupportedOperationException - if no MapMutator has been specified

java.lang.ClassCastException - if the class of the specified key or value prevents it from being stored in this map.

java.lang.IllegalArgumentException - if some aspect of this key or value prevents it from being stored in this map.

java.lang.NullPointerException - this map does not permit null keys or values, and the specified key or value is null.

putAll

public void putAll(java.util.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.

Specified by:

putAll in interface java.util.Map

Parameters:

map - Mappings to be stored in this map.

Throws:

java.lang.UnsupportedOperationException - if the putAll method is not supported by this map.

java.lang.ClassCastException - if the class of a key or value in the specified map prevents it from being stored in this map.

java.lang.IllegalArgumentException - some aspect of a key or value in the specified map prevents it from being stored in this map.

java.lang.NullPointerException - the specified map is null, or if this map does not permit null keys or values, and the specified map contains null keys or values.

remove

public java.lang.Object remove(java.lang.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.

Specified by:

remove in interface java.util.Map

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.

Throws:

java.lang.ClassCastException - if the key is of an inappropriate type for the composited map (optional).

java.lang.NullPointerException - if the key is null and the composited map does not not permit null keys (optional).

java.lang.UnsupportedOperationException - if the remove method is not supported by the composited map containing the key

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.

Specified by:

size in interface java.util.Map

Returns:

the number of key-value mappings in this map.

values

public java.util.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.

Specified by:

values in interface java.util.Map

Returns:

a collection view of the values contained in this map.

equals

public boolean equals(java.lang.Object obj)

Checks if this Map equals another as per the Map specification.

Specified by:

equals in interface java.util.Map

Overrides:

equals in class java.lang.Object

Parameters:

obj - the object to compare to

Returns:

true if the maps are equal

hashCode

public int hashCode()

Gets a hash code for the Map as per the Map specification.

Specified by:

hashCode in interface java.util.Map

Overrides:

hashCode in class java.lang.Object