org.apache.commons.collections.map

Class MultiKeyMap

java.lang.Object

org.apache.commons.collections.map.MultiKeyMap

All Implemented Interfaces:

java.io.Serializable, java.util.Map, IterableMap

public class MultiKeyMap
extends java.lang.Object
implements IterableMap, java.io.Serializable

A Map implementation that uses multiple keys to map the value.

This class is the most efficient way to uses multiple keys to map to a value. The best way to use this class is via the additional map-style methods. These provide get, containsKey, put and remove for individual keys which operate without extra object creation.

The additional methods are the main interface of this map. As such, you will not normally hold this map in a variable of type Map.

The normal map methods take in and return a MultiKey. If you try to use put() with any other object type a ClassCastException is thrown. If you try to use null as the key in put() a NullPointerException is thrown.

This map is implemented as a decorator of a AbstractHashedMap which enables extra behaviour to be added easily.

• MultiKeyMap.decorate(new LinkedMap()) creates an ordered map.
• MultiKeyMap.decorate(new LRUMap()) creates an least recently used map.
• MultiKeyMap.decorate(new ReferenceMap()) creates a garbage collector sensitive map.

Note that IdentityMap and ReferenceIdentityMap are unsuitable for use as the key comparison would work on the whole MultiKey, not the elements within.

As an example, consider a least recently used cache that uses a String airline code and a Locale to lookup the airline's name:

 private MultiKeyMap cache = MultiKeyMap.decorate(new LRUMap(50));
 
 public String getAirlineName(String code, String locale) {
   String name = (String) cache.get(code, locale);
   if (name == null) {
     name = getAirlineNameFromDB(code, locale);
     cache.put(code, locale, name);
   }
   return name;
 }
 

Note that MultiKeyMap is not synchronized and is not thread-safe. If you wish to use this map from multiple threads concurrently, you must use appropriate synchronization. This class may throw exceptions when accessed by concurrent threads without synchronization.

Since:

Commons Collections 3.1

See Also:

Serialized Form

Nested Class Summary

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

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

Constructor Summary

Constructors

Constructor and Description
MultiKeyMap() Constructs a new MultiKeyMap that decorates a HashedMap.

Method Summary

Modifier and Type	Method and Description
void	clear()
java.lang.Object	clone() Clones the map without cloning the keys or values.
boolean	containsKey(java.lang.Object key)
boolean	containsKey(java.lang.Object key1, java.lang.Object key2) Checks whether the map contains the specified multi-key.
boolean	containsKey(java.lang.Object key1, java.lang.Object key2, java.lang.Object key3) Checks whether the map contains the specified multi-key.
boolean	containsKey(java.lang.Object key1, java.lang.Object key2, java.lang.Object key3, java.lang.Object key4) Checks whether the map contains the specified multi-key.
boolean	containsKey(java.lang.Object key1, java.lang.Object key2, java.lang.Object key3, java.lang.Object key4, java.lang.Object key5) Checks whether the map contains the specified multi-key.
boolean	containsValue(java.lang.Object value)
static MultiKeyMap	decorate(AbstractHashedMap map) Decorates the specified map to add the MultiKeyMap API and fast query.
java.util.Set	entrySet()
boolean	equals(java.lang.Object obj)
java.lang.Object	get(java.lang.Object key)
java.lang.Object	get(java.lang.Object key1, java.lang.Object key2) Gets the value mapped to the specified multi-key.
java.lang.Object	get(java.lang.Object key1, java.lang.Object key2, java.lang.Object key3) Gets the value mapped to the specified multi-key.
java.lang.Object	get(java.lang.Object key1, java.lang.Object key2, java.lang.Object key3, java.lang.Object key4) Gets the value mapped to the specified multi-key.
java.lang.Object	get(java.lang.Object key1, java.lang.Object key2, java.lang.Object key3, java.lang.Object key4, java.lang.Object key5) Gets the value mapped to the specified multi-key.
int	hashCode()
boolean	isEmpty()
java.util.Set	keySet()
MapIterator	mapIterator() Obtains a MapIterator over the map.
java.lang.Object	put(java.lang.Object key, java.lang.Object value) Puts the key and value into the map, where the key must be a non-null MultiKey object.
java.lang.Object	put(java.lang.Object key1, java.lang.Object key2, java.lang.Object value) Stores the value against the specified multi-key.
java.lang.Object	put(java.lang.Object key1, java.lang.Object key2, java.lang.Object key3, java.lang.Object value) Stores the value against the specified multi-key.
java.lang.Object	put(java.lang.Object key1, java.lang.Object key2, java.lang.Object key3, java.lang.Object key4, java.lang.Object value) Stores the value against the specified multi-key.
java.lang.Object	put(java.lang.Object key1, java.lang.Object key2, java.lang.Object key3, java.lang.Object key4, java.lang.Object key5, java.lang.Object value) Stores the value against the specified multi-key.
void	putAll(java.util.Map mapToCopy) Copies all of the keys and values from the specified map to this map.
java.lang.Object	remove(java.lang.Object key)
java.lang.Object	remove(java.lang.Object key1, java.lang.Object key2) Removes the specified multi-key from this map.
java.lang.Object	remove(java.lang.Object key1, java.lang.Object key2, java.lang.Object key3) Removes the specified multi-key from this map.
java.lang.Object	remove(java.lang.Object key1, java.lang.Object key2, java.lang.Object key3, java.lang.Object key4) Removes the specified multi-key from this map.
java.lang.Object	remove(java.lang.Object key1, java.lang.Object key2, java.lang.Object key3, java.lang.Object key4, java.lang.Object key5) Removes the specified multi-key from this map.
boolean	removeAll(java.lang.Object key1) Removes all mappings where the first key is that specified.
boolean	removeAll(java.lang.Object key1, java.lang.Object key2) Removes all mappings where the first two keys are those specified.
boolean	removeAll(java.lang.Object key1, java.lang.Object key2, java.lang.Object key3) Removes all mappings where the first three keys are those specified.
boolean	removeAll(java.lang.Object key1, java.lang.Object key2, java.lang.Object key3, java.lang.Object key4) Removes all mappings where the first four keys are those specified.
int	size()
java.lang.String	toString()
java.util.Collection	values()

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.util.Map

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

Constructor Detail

MultiKeyMap

public MultiKeyMap()

Constructs a new MultiKeyMap that decorates a HashedMap.

Method Detail

decorate

public static MultiKeyMap decorate(AbstractHashedMap map)

Decorates the specified map to add the MultiKeyMap API and fast query. The map must not be null and must be empty.

Parameters:

map - the map to decorate, not null

Throws:

java.lang.IllegalArgumentException - if the map is null or not empty

get

public java.lang.Object get(java.lang.Object key1,
                            java.lang.Object key2)

Gets the value mapped to the specified multi-key.

Parameters:

key1 - the first key

key2 - the second key

Returns:

the mapped value, null if no match

containsKey

public boolean containsKey(java.lang.Object key1,
                           java.lang.Object key2)

Checks whether the map contains the specified multi-key.

Parameters:

key1 - the first key

key2 - the second key

Returns:

true if the map contains the key

put

public java.lang.Object put(java.lang.Object key1,
                            java.lang.Object key2,
                            java.lang.Object value)

Stores the value against the specified multi-key.

Parameters:

key1 - the first key

key2 - the second key

value - the value to store

Returns:

the value previously mapped to this combined key, null if none

remove

public java.lang.Object remove(java.lang.Object key1,
                               java.lang.Object key2)

Removes the specified multi-key from this map.

Specified by:

remove in interface java.util.Map

Parameters:

key1 - the first key

key2 - the second key

Returns:

the value mapped to the removed key, null if key not in map

get

public java.lang.Object get(java.lang.Object key1,
                            java.lang.Object key2,
                            java.lang.Object key3)

Gets the value mapped to the specified multi-key.

Parameters:

key1 - the first key

key2 - the second key

key3 - the third key

Returns:

the mapped value, null if no match

containsKey

public boolean containsKey(java.lang.Object key1,
                           java.lang.Object key2,
                           java.lang.Object key3)

Checks whether the map contains the specified multi-key.

Parameters:

key1 - the first key

key2 - the second key

key3 - the third key

Returns:

true if the map contains the key

put

public java.lang.Object put(java.lang.Object key1,
                            java.lang.Object key2,
                            java.lang.Object key3,
                            java.lang.Object value)

Stores the value against the specified multi-key.

Parameters:

key1 - the first key

key2 - the second key

key3 - the third key

value - the value to store

Returns:

the value previously mapped to this combined key, null if none

remove

public java.lang.Object remove(java.lang.Object key1,
                               java.lang.Object key2,
                               java.lang.Object key3)

Removes the specified multi-key from this map.

Parameters:

key1 - the first key

key2 - the second key

key3 - the third key

Returns:

the value mapped to the removed key, null if key not in map

get

public java.lang.Object get(java.lang.Object key1,
                            java.lang.Object key2,
                            java.lang.Object key3,
                            java.lang.Object key4)

Gets the value mapped to the specified multi-key.

Parameters:

key1 - the first key

key2 - the second key

key3 - the third key

key4 - the fourth key

Returns:

the mapped value, null if no match

containsKey

public boolean containsKey(java.lang.Object key1,
                           java.lang.Object key2,
                           java.lang.Object key3,
                           java.lang.Object key4)

Checks whether the map contains the specified multi-key.

Parameters:

key1 - the first key

key2 - the second key

key3 - the third key

key4 - the fourth key

Returns:

true if the map contains the key

put

public java.lang.Object put(java.lang.Object key1,
                            java.lang.Object key2,
                            java.lang.Object key3,
                            java.lang.Object key4,
                            java.lang.Object value)

Stores the value against the specified multi-key.

Parameters:

key1 - the first key

key2 - the second key

key3 - the third key

key4 - the fourth key

value - the value to store

Returns:

the value previously mapped to this combined key, null if none

remove

public java.lang.Object remove(java.lang.Object key1,
                               java.lang.Object key2,
                               java.lang.Object key3,
                               java.lang.Object key4)

Removes the specified multi-key from this map.

Parameters:

key1 - the first key

key2 - the second key

key3 - the third key

key4 - the fourth key

Returns:

the value mapped to the removed key, null if key not in map

get

public java.lang.Object get(java.lang.Object key1,
                            java.lang.Object key2,
                            java.lang.Object key3,
                            java.lang.Object key4,
                            java.lang.Object key5)

Gets the value mapped to the specified multi-key.

Parameters:

key1 - the first key

key2 - the second key

key3 - the third key

key4 - the fourth key

key5 - the fifth key

Returns:

the mapped value, null if no match

containsKey

public boolean containsKey(java.lang.Object key1,
                           java.lang.Object key2,
                           java.lang.Object key3,
                           java.lang.Object key4,
                           java.lang.Object key5)

Checks whether the map contains the specified multi-key.

Parameters:

key1 - the first key

key2 - the second key

key3 - the third key

key4 - the fourth key

key5 - the fifth key

Returns:

true if the map contains the key

put

public java.lang.Object put(java.lang.Object key1,
                            java.lang.Object key2,
                            java.lang.Object key3,
                            java.lang.Object key4,
                            java.lang.Object key5,
                            java.lang.Object value)

Stores the value against the specified multi-key.

Parameters:

key1 - the first key

key2 - the second key

key3 - the third key

key4 - the fourth key

key5 - the fifth key

value - the value to store

Returns:

the value previously mapped to this combined key, null if none

remove

public java.lang.Object remove(java.lang.Object key1,
                               java.lang.Object key2,
                               java.lang.Object key3,
                               java.lang.Object key4,
                               java.lang.Object key5)

Removes the specified multi-key from this map.

Parameters:

key1 - the first key

key2 - the second key

key3 - the third key

key4 - the fourth key

key5 - the fifth key

Returns:

the value mapped to the removed key, null if key not in map

removeAll

public boolean removeAll(java.lang.Object key1)

Removes all mappings where the first key is that specified.

This method removes all the mappings where the MultiKey has one or more keys, and the first matches that specified.

Parameters:

key1 - the first key

Returns:

true if any elements were removed

removeAll

public boolean removeAll(java.lang.Object key1,
                         java.lang.Object key2)

Removes all mappings where the first two keys are those specified.

This method removes all the mappings where the MultiKey has two or more keys, and the first two match those specified.

Parameters:

key1 - the first key

key2 - the second key

Returns:

true if any elements were removed

removeAll

public boolean removeAll(java.lang.Object key1,
                         java.lang.Object key2,
                         java.lang.Object key3)

Removes all mappings where the first three keys are those specified.

This method removes all the mappings where the MultiKey has three or more keys, and the first three match those specified.

Parameters:

key1 - the first key

key2 - the second key

key3 - the third key

Returns:

true if any elements were removed

removeAll

public boolean removeAll(java.lang.Object key1,
                         java.lang.Object key2,
                         java.lang.Object key3,
                         java.lang.Object key4)

Removes all mappings where the first four keys are those specified.

This method removes all the mappings where the MultiKey has four or more keys, and the first four match those specified.

Parameters:

key1 - the first key

key2 - the second key

key3 - the third key

key4 - the fourth key

Returns:

true if any elements were removed

clone

public java.lang.Object clone()

Clones the map without cloning the keys or values.

Overrides:

clone in class java.lang.Object

Returns:

a shallow clone

put

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

Puts the key and value into the map, where the key must be a non-null MultiKey object.

Specified by:

put in interface java.util.Map

Parameters:

key - the non-null MultiKey object

value - the value to store

Returns:

the previous value for the key

Throws:

java.lang.NullPointerException - if the key is null

java.lang.ClassCastException - if the key is not a MultiKey

putAll

public void putAll(java.util.Map mapToCopy)

Copies all of the keys and values from the specified map to this map. Each key must be non-null and a MultiKey object.

Specified by:

putAll in interface java.util.Map

Parameters:

mapToCopy - to this map

Throws:

java.lang.NullPointerException - if the mapToCopy or any key within is null

java.lang.ClassCastException - if any key in mapToCopy is not a MultiKey

mapIterator

public MapIterator mapIterator()

Description copied from interface: IterableMap

Obtains a MapIterator over the map.

A map iterator is an efficient way of iterating over maps. There is no need to access the entry set or cast to Map Entry objects.

 IterableMap map = new HashedMap();
 MapIterator it = map.mapIterator();
 while (it.hasNext()) {
   Object key = it.next();
   Object value = it.getValue();
   it.setValue("newValue");
 }
 

Specified by:

mapIterator in interface IterableMap

Returns:

a map iterator

size

public int size()

Specified by:

size in interface java.util.Map

isEmpty

public boolean isEmpty()

Specified by:

isEmpty in interface java.util.Map

containsKey

public boolean containsKey(java.lang.Object key)

Specified by:

containsKey in interface java.util.Map

containsValue

public boolean containsValue(java.lang.Object value)

Specified by:

containsValue in interface java.util.Map

get

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

Specified by:

get in interface java.util.Map

remove

public java.lang.Object remove(java.lang.Object key)

Specified by:

remove in interface java.util.Map

clear

public void clear()

Specified by:

clear in interface java.util.Map

keySet

public java.util.Set keySet()

Specified by:

keySet in interface java.util.Map

values

public java.util.Collection values()

Specified by:

values in interface java.util.Map

entrySet

public java.util.Set entrySet()

Specified by:

entrySet in interface java.util.Map

equals

public boolean equals(java.lang.Object obj)

Specified by:

equals in interface java.util.Map

Overrides:

equals in class java.lang.Object

hashCode

public int hashCode()

Specified by:

hashCode in interface java.util.Map

Overrides:

hashCode in class java.lang.Object

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object