uk.co.strangeskies.collection.computingmap

Class ComputingHashMap<K,V>

java.lang.Object

uk.co.strangeskies.collection.computingmap.ComputingHashMap<K,V>

All Implemented Interfaces:

ComputingMap<K,V>, ReadOnlyMap<K,V>

public class ComputingHashMap<K,V>
extends java.lang.Object
implements ComputingMap<K,V>

Constructor Summary

Constructors

Constructor and Description
ComputingHashMap(java.util.function.Function<K,V> computation)

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.
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 ComputingMap.get(K).
V	putGet(K key, java.util.function.Consumer<V> wasPresent, java.util.function.Consumer<V> wasMissing)
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 class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

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

isEmpty, putAll, putGet, remove, removeAll

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

size

Constructor Detail

ComputingHashMap

public ComputingHashMap(java.util.function.Function<K,V> computation)

Method Detail

get

public V get(K key)

Description copied from interface: ComputingMap

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 ComputingMap<K,V>

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

public boolean put(K key)

Description copied from interface: ComputingMap

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 ComputingMap.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.

Specified by:

put in interface ComputingMap<K,V>

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

putGet

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

Specified by:

putGet in interface ComputingMap<K,V>

keySet

public java.util.Set<K> keySet()

Specified by:

keySet in interface ComputingMap<K,V>

Specified by:

keySet in interface ReadOnlyMap<K,V>

values

public java.util.Collection<V> values()

Specified by:

values in interface ComputingMap<K,V>

removeGet

public V removeGet(K key)

Description copied from interface: ComputingMap

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

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

Specified by:

removeGet in interface ComputingMap<K,V>

Parameters:

key - The key to remove.

Returns:

The value removed.

clear

public boolean clear()

Description copied from interface: ComputingMap

Remove all keys and values from the map.

Specified by:

clear in interface ComputingMap<K,V>

Returns:

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