com.arellomobile.mvp

Class WeakValueHashMap<K,V>

java.lang.Object

java.util.AbstractMap<K,V>

com.arellomobile.mvp.WeakValueHashMap<K,V>

Type Parameters:

K - - the type of the key object

V - - the type of the value object

All Implemented Interfaces:

java.util.Map<K,V>

public class WeakValueHashMap<K,V>
extends java.util.AbstractMap<K,V>

The desired behaviour of an in-memory cache is to keep a weak reference to the cached object, this will allow the garbage collector to remove an object from memory once it isn't needed anymore.

A HashMap doesn't help here since it will keep hard references for key and value objects. A WeakHashMap doesn't either, because it keeps weak references to the key objects, but we want to track the value objects.

This implementation of a Map uses a WeakReference to the value objects. Once the garbage collector decides it wants to finalize a value object, it will be removed from the map automatically.

Nested Class Summary

Nested classes/interfaces inherited from class java.util.AbstractMap

java.util.AbstractMap.SimpleEntry<K,V>, java.util.AbstractMap.SimpleImmutableEntry<K,V>

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

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

Constructor Summary

Constructors

Constructor and Description
WeakValueHashMap() Creates a WeakValueHashMap with an initial capacity of 1
WeakValueHashMap(int capacity) Creates a WeakValueHashMap with a desired initial capacity
WeakValueHashMap(java.util.Map<? extends K,? extends V> map) Creates a WeakValueHashMap and copies the content from an existing map

Method Summary

Modifier and Type	Method and Description
void	clear()
boolean	containsKey(java.lang.Object key)
boolean	containsValue(java.lang.Object value)
java.util.Set<java.util.Map.Entry<K,V>>	entrySet()
V	get(java.lang.Object key)
java.util.Set<K>	keySet()
V	put(K key, V value)
V	remove(java.lang.Object key)
int	size()
java.util.Collection<V>	values()

Methods inherited from class java.util.AbstractMap

clone, equals, hashCode, isEmpty, putAll, toString

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.util.Map

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

Constructor Detail

WeakValueHashMap

public WeakValueHashMap(int capacity)

Creates a WeakValueHashMap with a desired initial capacity

Parameters:

capacity - - the initial capacity

WeakValueHashMap

public WeakValueHashMap()

Creates a WeakValueHashMap with an initial capacity of 1

WeakValueHashMap

public WeakValueHashMap(java.util.Map<? extends K,? extends V> map)

Creates a WeakValueHashMap and copies the content from an existing map

Parameters:

map - - the map to copy from

Method Detail

put

public V put(K key,
             V value)

Specified by:

put in interface java.util.Map<K,V>

Overrides:

put in class java.util.AbstractMap<K,V>

get

public V get(java.lang.Object key)

Specified by:

get in interface java.util.Map<K,V>

Overrides:

get in class java.util.AbstractMap<K,V>

remove

public V remove(java.lang.Object key)

Specified by:

remove in interface java.util.Map<K,V>

Overrides:

remove in class java.util.AbstractMap<K,V>

clear

public void clear()

Specified by:

clear in interface java.util.Map<K,V>

Overrides:

clear in class java.util.AbstractMap<K,V>

containsKey

public boolean containsKey(java.lang.Object key)

Specified by:

containsKey in interface java.util.Map<K,V>

Overrides:

containsKey in class java.util.AbstractMap<K,V>

containsValue

public boolean containsValue(java.lang.Object value)

Specified by:

containsValue in interface java.util.Map<K,V>

Overrides:

containsValue in class java.util.AbstractMap<K,V>

keySet

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

Specified by:

keySet in interface java.util.Map<K,V>

Overrides:

keySet in class java.util.AbstractMap<K,V>

size

public int size()

Specified by:

size in interface java.util.Map<K,V>

Overrides:

size in class java.util.AbstractMap<K,V>

entrySet

public java.util.Set<java.util.Map.Entry<K,V>> entrySet()

Specified by:

entrySet in interface java.util.Map<K,V>

Specified by:

entrySet in class java.util.AbstractMap<K,V>

values

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

Specified by:

values in interface java.util.Map<K,V>

Overrides:

values in class java.util.AbstractMap<K,V>