org.apache.commons.collections.map

Class MultiKeyMap

Implemented Interfaces:
IterableMap, Map, Serializable

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

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;
 }
 
Version:
$Revision: 1.3 $ $Date: 2004/06/07 21:00:58 $
Author:
Stephen Colebourne
Since:
Commons Collections 3.1

Field Summary

protected AbstractHashedMap
map
The decorated map

Constructor Summary

MultiKeyMap()
Constructs a new MultiKeyMap that decorates a HashedMap.
MultiKeyMap(AbstractHashedMap map)
Constructor that decorates the specified map and is called from decorate(AbstractHashedMap).

Method Summary

protected void
checkKey(Object key)
Check to ensure that input keys are valid MultiKey objects.
void
clear()
Object
clone()
Clones the map without cloning the keys or values.
boolean
containsKey(Object key)
boolean
containsKey(Object key1, Object key2)
Checks whether the map contains the specified multi-key.
boolean
containsKey(Object key1, Object key2, Object key3)
Checks whether the map contains the specified multi-key.
boolean
containsKey(Object key1, Object key2, Object key3, Object key4)
Checks whether the map contains the specified multi-key.
boolean
containsKey(Object key1, Object key2, Object key3, Object key4, Object key5)
Checks whether the map contains the specified multi-key.
boolean
containsValue(Object value)
static MultiKeyMap
decorate(AbstractHashedMap map)
Decorates the specified map to add the MultiKeyMap API and fast query.
Set
entrySet()
boolean
equals(Object obj)
Object
get(Object key)
Object
get(Object key1, Object key2)
Gets the value mapped to the specified multi-key.
Object
get(Object key1, Object key2, Object key3)
Gets the value mapped to the specified multi-key.
Object
get(Object key1, Object key2, Object key3, Object key4)
Gets the value mapped to the specified multi-key.
Object
get(Object key1, Object key2, Object key3, Object key4, Object key5)
Gets the value mapped to the specified multi-key.
protected int
hash(Object key1, Object key2)
Gets the hash code for the specified multi-key.
protected int
hash(Object key1, Object key2, Object key3)
Gets the hash code for the specified multi-key.
protected int
hash(Object key1, Object key2, Object key3, Object key4)
Gets the hash code for the specified multi-key.
protected int
hash(Object key1, Object key2, Object key3, Object key4, Object key5)
Gets the hash code for the specified multi-key.
int
hashCode()
boolean
isEmpty()
protected boolean
isEqualKey(AbstractHashedMap.HashEntry entry, Object key1, Object key2)
Is the key equal to the combined key.
protected boolean
isEqualKey(AbstractHashedMap.HashEntry entry, Object key1, Object key2, Object key3)
Is the key equal to the combined key.
protected boolean
isEqualKey(AbstractHashedMap.HashEntry entry, Object key1, Object key2, Object key3, Object key4)
Is the key equal to the combined key.
protected boolean
isEqualKey(AbstractHashedMap.HashEntry entry, Object key1, Object key2, Object key3, Object key4, Object key5)
Is the key equal to the combined key.
Set
keySet()
MapIterator
mapIterator()
Obtains a MapIterator over the map.
Object
put(Object key, Object value)
Puts the key and value into the map, where the key must be a non-null MultiKey object.
Object
put(Object key1, Object key2, Object value)
Stores the value against the specified multi-key.
Object
put(Object key1, Object key2, Object key3, Object value)
Stores the value against the specified multi-key.
Object
put(Object key1, Object key2, Object key3, Object key4, Object value)
Stores the value against the specified multi-key.
Object
put(Object key1, Object key2, Object key3, Object key4, Object key5, Object value)
Stores the value against the specified multi-key.
void
putAll(Map mapToCopy)
Puts all the keys and values into this map.
Object
remove(Object key)
Object
remove(Object key1, Object key2)
Removes the specified multi-key from this map.
Object
remove(Object key1, Object key2, Object key3)
Removes the specified multi-key from this map.
Object
remove(Object key1, Object key2, Object key3, Object key4)
Removes the specified multi-key from this map.
Object
remove(Object key1, Object key2, Object key3, Object key4, Object key5)
Removes the specified multi-key from this map.
boolean
removeAll(Object key1)
Removes all mappings where the first key is that specified.
boolean
removeAll(Object key1, Object key2)
Removes all mappings where the first two keys are those specified.
boolean
removeAll(Object key1, Object key2, Object key3)
Removes all mappings where the first three keys are those specified.
boolean
removeAll(Object key1, Object key2, Object key3, Object key4)
Removes all mappings where the first four keys are those specified.
int
size()
String
toString()
Collection
values()

Field Details

map

protected final AbstractHashedMap map
The decorated map

Constructor Details

MultiKeyMap

public MultiKeyMap()
Constructs a new MultiKeyMap that decorates a HashedMap.

MultiKeyMap

protected MultiKeyMap(AbstractHashedMap map)
Constructor that decorates the specified map and is called from decorate(AbstractHashedMap). The map must not be null and should be empty or only contain valid keys. This constructor performs no validation.
Parameters:
map - the map to decorate

Method Details

checkKey

protected void checkKey(Object key)
Check to ensure that input keys are valid MultiKey objects.
Parameters:
key - the key to check

clear

public void clear()

clone

public Object clone()
Clones the map without cloning the keys or values.
Returns:
a shallow clone

containsKey

public boolean containsKey(Object key)

containsKey

public boolean containsKey(Object key1,
                           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

containsKey

public boolean containsKey(Object key1,
                           Object key2,
                           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

containsKey

public boolean containsKey(Object key1,
                           Object key2,
                           Object key3,
                           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

containsKey

public boolean containsKey(Object key1,
                           Object key2,
                           Object key3,
                           Object key4,
                           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

containsValue

public boolean containsValue(Object value)

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

entrySet

public Set entrySet()

equals

public boolean equals(Object obj)

get

public Object get(Object key)

get

public Object get(Object key1,
                  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

get

public Object get(Object key1,
                  Object key2,
                  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

get

public Object get(Object key1,
                  Object key2,
                  Object key3,
                  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

get

public Object get(Object key1,
                  Object key2,
                  Object key3,
                  Object key4,
                  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

hash

protected int hash(Object key1,
                   Object key2)
Gets the hash code for the specified multi-key.
Parameters:
key1 - the first key
key2 - the second key
Returns:
the hash code

hash

protected int hash(Object key1,
                   Object key2,
                   Object key3)
Gets the hash code for the specified multi-key.
Parameters:
key1 - the first key
key2 - the second key
key3 - the third key
Returns:
the hash code

hash

protected int hash(Object key1,
                   Object key2,
                   Object key3,
                   Object key4)
Gets the hash code for the specified multi-key.
Parameters:
key1 - the first key
key2 - the second key
key3 - the third key
key4 - the fourth key
Returns:
the hash code

hash

protected int hash(Object key1,
                   Object key2,
                   Object key3,
                   Object key4,
                   Object key5)
Gets the hash code for 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 hash code

hashCode

public int hashCode()

isEmpty

public boolean isEmpty()

isEqualKey

protected boolean isEqualKey(AbstractHashedMap.HashEntry entry,
                             Object key1,
                             Object key2)
Is the key equal to the combined key.
Parameters:
entry - the entry to compare to
key1 - the first key
key2 - the second key
Returns:
true if the key matches

isEqualKey

protected boolean isEqualKey(AbstractHashedMap.HashEntry entry,
                             Object key1,
                             Object key2,
                             Object key3)
Is the key equal to the combined key.
Parameters:
entry - the entry to compare to
key1 - the first key
key2 - the second key
key3 - the third key
Returns:
true if the key matches

isEqualKey

protected boolean isEqualKey(AbstractHashedMap.HashEntry entry,
                             Object key1,
                             Object key2,
                             Object key3,
                             Object key4)
Is the key equal to the combined key.
Parameters:
entry - the entry to compare to
key1 - the first key
key2 - the second key
key3 - the third key
key4 - the fourth key
Returns:
true if the key matches

isEqualKey

protected boolean isEqualKey(AbstractHashedMap.HashEntry entry,
                             Object key1,
                             Object key2,
                             Object key3,
                             Object key4,
                             Object key5)
Is the key equal to the combined key.
Parameters:
entry - the entry to compare to
key1 - the first key
key2 - the second key
key3 - the third key
key4 - the fourth key
key5 - the fifth key
Returns:
true if the key matches

keySet

public Set keySet()

mapIterator

public MapIterator mapIterator()
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

put

public Object put(Object key,
                  Object value)
Puts the key and value into the map, where the key must be a non-null MultiKey object.
Parameters:
key - the non-null MultiKey object
value - the value to store
Returns:
the previous value for the key

put

public Object put(Object key1,
                  Object key2,
                  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

put

public Object put(Object key1,
                  Object key2,
                  Object key3,
                  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

put

public Object put(Object key1,
                  Object key2,
                  Object key3,
                  Object key4,
                  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

put

public Object put(Object key1,
                  Object key2,
                  Object key3,
                  Object key4,
                  Object key5,
                  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

putAll

public void putAll(Map mapToCopy)
Puts all the keys and values into this map. Each key must be non-null and a MultiKey object.
Parameters:

remove

public Object remove(Object key)

remove

public Object remove(Object key1,
                     Object key2)
Removes the specified multi-key from this map.
Parameters:
key1 - the first key
key2 - the second key
Returns:
the value mapped to the removed key, null if key not in map

remove

public Object remove(Object key1,
                     Object key2,
                     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

remove

public Object remove(Object key1,
                     Object key2,
                     Object key3,
                     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

remove

public Object remove(Object key1,
                     Object key2,
                     Object key3,
                     Object key4,
                     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(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(Object key1,
                         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(Object key1,
                         Object key2,
                         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(Object key1,
                         Object key2,
                         Object key3,
                         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

size

public int size()

toString

public String toString()

values

public Collection values()

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