uk.co.strangeskies.collection.computingmap

Interface ComputingMap<K,V>

Type Parameters:

V - The type of values

K - The type of keys

All Superinterfaces:

ReadOnlyMap<K,V>

All Known Implementing Classes:

CacheComputingMap, ComputingEntryHashMap, ComputingHashMap, DeferredComputingMap, FutureMap, LRUCacheComputingMap

public interface ComputingMap<K,V>
extends ReadOnlyMap<K,V>

Conceptually, this map behaves much like an ordinary map other than the semantics of putting a key value pair into the map. A ComputingMap is associated with a particular computation - which effectively is equivalent to a function from type K to type V. This means that we may simply add a key to the map and have the associated value be calculated and added automatically. This interface may form the basis of a caching system, for example.

Method Summary

Modifier and Type	Method and Description
boolean	clear() Remove all keys and values from the map.
V	get(K key) For the given key, this method should return the value which has been computed.
default boolean	isEmpty()
java.util.Set<K>	keySet()
boolean	put(K key) Enters the key into the map such that a value of type V will at some point be computed which will be then returned by any subsequent calls to get(K).
default boolean	putAll(java.util.Collection<? extends K> keys)
default V	putGet(K key) This method simply makes sure the value for the given key has been computed and added to the map, then returns it.
V	putGet(K key, java.util.function.Consumer<V> wasPresent, java.util.function.Consumer<V> wasMissing)
default boolean	remove(K key) Remove the given key and it's associated computed value from the map.
default boolean	removeAll(java.util.Collection<? extends K> keys)
V	removeGet(K key) Remove the given key and it's associated computed value from the map.
java.util.Collection<V>	values()

Methods inherited from interface uk.co.strangeskies.collection.computingmap.ReadOnlyMap

size

Method Detail

get

V get(K key)

For the given key, this method should return the value which has been computed. This interface, by contract, provides no guarantees that the value for a previously entered key will still be contained within the map. Despite this, for keys which have not yet been entered into the map, an invocation of this method should simply return null, rather than attempting to compute the given value and then return it. Implementations are, of course, free to provide this guarantee.

Specified by:

get in interface ReadOnlyMap<K,V>

Parameters:

key - The key object for which to return the mapped computed value

Returns:

The computed value associated with a given key

put

boolean put(K key)

Enters the key into the map such that a value of type V will at some point be computed which will be then returned by any subsequent calls to get(K). Generally keys should be immutable, and the computation associated with the map will be expected to produce identical results each time, so in the case that the key has already been added to the map most implementations should just return instantly and do no work. Because of this it also makes little sense to return the previous value for a key entered more than once.

Parameters:

key - The key object to be mapped to a new value

Returns:

True if the associated value was not already contained in the map, false otherwise

putAll

default boolean putAll(java.util.Collection<? extends K> keys)

putGet

default V putGet(K key)

This method simply makes sure the value for the given key has been computed and added to the map, then returns it.

Parameters:

key - The key object to be mapped to a new value

Returns:

The computed value associated with a given key.

putGet

V putGet(K key,
         java.util.function.Consumer<V> wasPresent,
         java.util.function.Consumer<V> wasMissing)

keySet

java.util.Set<K> keySet()

Specified by:

keySet in interface ReadOnlyMap<K,V>

values

java.util.Collection<V> values()

removeGet

V removeGet(K key)

Remove the given key and it's associated computed value from the map.

Use of this method may result in worse performance that remove(Object), as some implementations may cancel value computation for keys removed by the latter.

Parameters:

key - The key to remove.

Returns:

The value removed.

remove

default boolean remove(K key)

Remove the given key and it's associated computed value from the map.

Parameters:

key - The key to remove.

Returns:

True if the key was in the map, false otherwise.

removeAll

default boolean removeAll(java.util.Collection<? extends K> keys)

clear

boolean clear()

Remove all keys and values from the map.

Returns:

True if the map contained keys, false if it was empty.

isEmpty

default boolean isEmpty()

Specified by:

isEmpty in interface ReadOnlyMap<K,V>