Package org.apache.commons.collections4.map

Class MultiKeyMap<K,V>

java.lang.Object
org.apache.commons.collections4.map.AbstractIterableMap<K,V>
org.apache.commons.collections4.map.AbstractMapDecorator<MultiKey<? extends K>,V>
org.apache.commons.collections4.map.MultiKeyMap<K,V>
Type Parameters:
K - the type of the keys in this map
V - the type of the values in this map
All Implemented Interfaces:
Serializable, Cloneable, Map<MultiKey<? extends K>,V>, Get<MultiKey<? extends K>,V>, IterableGet<MultiKey<? extends K>,V>, IterableMap<MultiKey<? extends K>,V>, Put<MultiKey<? extends K>,V>
public class MultiKeyMap<K,V> extends AbstractMapDecorator<MultiKey<? extends K>,V> implements Serializable, Cloneable
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 behavior 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.multiKeyMap(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:
3.1
See Also:

  • Constructor Details

    • MultiKeyMap

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

    • MultiKeyMap

      protected MultiKeyMap(AbstractHashedMap<MultiKey<? extends K>,V> map)
      Constructor that decorates the specified map and is called from multiKeyMap(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

    • multiKeyMap

      public static <K, V> MultiKeyMap<K,V> multiKeyMap(AbstractHashedMap<MultiKey<? extends K>,V> map)
      Decorates the specified map to add the MultiKeyMap API and fast query. The map must not be null and must be empty.
      Type Parameters:
      K - the key type
      V - the value type
      Parameters:
      map - the map to decorate, not null
      Returns:
      a new multi key map
      Throws:
      NullPointerException - if map is null
      IllegalArgumentException - if the map is not empty
      Since:
      4.0

    • checkKey

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

    • clone

      public MultiKeyMap<K,V> clone()
      Clones the map without cloning the keys or values.
      Overrides:
      clone in class Object
      Returns:
      a shallow clone

    • 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

    • decorated

      protected AbstractHashedMap<MultiKey<? extends K>,V> decorated()
      Gets the map being decorated.
      Overrides:
      decorated in class AbstractMapDecorator<MultiKey<? extends K>,V>
      Returns:
      the decorated map

    • get

      public V 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 V 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 V 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 V 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

    • isEqualKey

      protected boolean isEqualKey(AbstractHashedMap.HashEntry<MultiKey<? extends K>,V> 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<MultiKey<? extends K>,V> 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<MultiKey<? extends K>,V> 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<MultiKey<? extends K>,V> 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

    • mapIterator

      public MapIterator<MultiKey<? extends K>,V> mapIterator()
      Description copied from class: AbstractIterableMap
      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 use Map Entry objects. 

       IterableMap<String,Integer> map = new HashedMap<String,Integer>();
 MapIterator<String,Integer> it = map.mapIterator();
 while (it.hasNext()) {
   String key = it.next();
   Integer value = it.getValue();
   it.setValue(value + 1);
 }
      Specified by:
      mapIterator in interface IterableGet<K,V>
      Overrides:
      mapIterator in class AbstractIterableMap<MultiKey<? extends K>,V>
      Returns:
      a map iterator

    • put

      public V put(K key1, K key2, K key3, K key4, K key5, V 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

    • put

      public V put(K key1, K key2, K key3, K key4, V 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 V put(K key1, K key2, K key3, V 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 V put(K key1, K key2, V 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 V put(MultiKey<? extends K> key, V value)
      Puts the key and value into the map, where the key must be a non-null MultiKey object.
      Specified by:
      put in interface Map<K,V>
      Specified by:
      put in interface Put<K,V>
      Overrides:
      put in class AbstractMapDecorator<MultiKey<? extends K>,V>
      Parameters:
      key - the non-null MultiKey object
      value - the value to store
      Returns:
      the previous value for the key
      Throws:
      NullPointerException - if the key is null
      ClassCastException - if the key is not a MultiKey
      See Also:

    • putAll

      public void putAll(Map<? extends MultiKey<? extends K>,? extends V> 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 Map<K,V>
      Specified by:
      putAll in interface Put<K,V>
      Overrides:
      putAll in class AbstractMapDecorator<MultiKey<? extends K>,V>
      Parameters:
      mapToCopy - to this map
      Throws:
      NullPointerException - if the mapToCopy or any key within is null
      ClassCastException - if any key in mapToCopy is not a MultiKey
      See Also:

    • 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

    • removeMultiKey

      public V removeMultiKey(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
      Since:
      4.0 (previous name: remove(Object, Object))

    • removeMultiKey

      public V removeMultiKey(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
      Since:
      4.0 (previous name: remove(Object, Object, Object))

    • removeMultiKey

      public V removeMultiKey(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
      Since:
      4.0 (previous name: remove(Object, Object, Object, Object))

    • removeMultiKey

      public V removeMultiKey(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
      Since:
      4.0 (previous name: remove(Object, Object, Object, Object, Object))