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Android Reference

WeakHashMap

java.util

Class WeakHashMap<K,V>

java.lang.Object
- java.util.AbstractMap<K,V>
- - java.util.WeakHashMap<K,V>

All Implemented Interfaces:

Map<K,V>
```
public class WeakHashMap<K,V>
extends AbstractMap<K,V>
implements Map<K,V>
```
WeakHashMap is an implementation of Map with keys which are WeakReferences. A key/value mapping is removed when the key is no longer referenced. All optional operations (adding and removing) are supported. Keys and values can be any objects. Note that the garbage collector acts similar to a second thread on this collection, possibly removing keys.

Since:

1.2

See Also:
HashMap, WeakReference

Nested Class Summary
- Nested classes/interfaces inherited from class java.util.AbstractMap
  AbstractMap.SimpleEntry<K,V>, AbstractMap.SimpleImmutableEntry<K,V>

Constructor Summary

Constructors
Constructor and Description
`WeakHashMap()` Constructs a new empty `WeakHashMap` instance.
`WeakHashMap(int capacity)` Constructs a new `WeakHashMap` instance with the specified capacity.
`WeakHashMap(int capacity, float loadFactor)` Constructs a new `WeakHashMap` instance with the specified capacity and load factor.
`WeakHashMap(Map<? extends K,? extends V> map)` Constructs a new `WeakHashMap` instance containing the mappings from the specified map.

Method Summary

Methods
Modifier and Type	Method and Description
`void`	`clear()` Removes all mappings from this map, leaving it empty.
`boolean`	`containsKey(Object key)` Returns whether this map contains the specified key.
`boolean`	`containsValue(Object value)` Returns whether this map contains the specified value.
`Set<Map.Entry<K,V>>`	`entrySet()` Returns a set containing all of the mappings in this map.
`V`	`get(Object key)` Returns the value of the mapping with the specified key.
`boolean`	`isEmpty()` Returns the number of elements in this map.
`Set<K>`	`keySet()` Returns a set of the keys contained in this map.
`V`	`put(K key, V value)` Maps the specified key to the specified value.
`void`	`putAll(Map<? extends K,? extends V> map)` Copies all the mappings in the given map to this map.
`V`	`remove(Object key)` Removes the mapping with the specified key from this map.
`int`	`size()` Returns the number of elements in this map.
`Collection<V>`	`values()` Returns a collection of the values contained in this map.

Methods inherited from class java.util.AbstractMap
clone, equals, hashCode, toString

Methods inherited from class java.lang.Object
finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.util.Map
equals, hashCode

- Constructor Detail
  - WeakHashMap
```
public WeakHashMap()
```
    Constructs a new empty WeakHashMap instance.
  - WeakHashMap
```
public WeakHashMap(int capacity)
```
    Constructs a new WeakHashMap instance with the specified capacity.
    
    Parameters:
    capacity - the initial capacity of this map.
    
    Throws:
    
    IllegalArgumentException - if the capacity is less than zero.
  - WeakHashMap
```
public WeakHashMap(int capacity,
           float loadFactor)
```
    Constructs a new WeakHashMap instance with the specified capacity and load factor.
    
    Parameters:
    capacity - the initial capacity of this map.
    loadFactor - the initial load factor.
    
    Throws:
    
    IllegalArgumentException - if the capacity is less than zero or the load factor is less or equal to zero.
  - WeakHashMap
```
public WeakHashMap(Map<? extends K,? extends V> map)
```
    Constructs a new WeakHashMap instance containing the mappings from the specified map.
    
    Parameters:
    map - the mappings to add.
- Method Detail
  - clear
```
public void clear()
```
    Removes all mappings from this map, leaving it empty.
    
    Specified by:
    
    clear in interface Map<K,V>
    
    Overrides:
    
    clear in class AbstractMap<K,V>
    
    See Also:
    isEmpty(), size()
  - containsKey
```
public boolean containsKey(Object key)
```
    Returns whether this map contains the specified key.
    
    Specified by:
    
    containsKey in interface Map<K,V>
    
    Overrides:
    
    containsKey in class AbstractMap<K,V>
    
    Parameters:
    key - the key to search for.
    
    Returns:
    true if this map contains the specified key, false otherwise.
  - entrySet
```
public Set<Map.Entry<K,V>> entrySet()
```
    Returns a set containing all of the mappings in this map. Each mapping is an instance of Map.Entry. As the set is backed by this map, changes in one will be reflected in the other. It does not support adding operations.
    
    Specified by:
    
    entrySet in interface Map<K,V>
    
    Specified by:
    
    entrySet in class AbstractMap<K,V>
    
    Returns:
    a set of the mappings.
  - keySet
```
public Set<K> keySet()
```
    Returns a set of the keys contained in this map. The set is backed by this map so changes to one are reflected by the other. The set does not support adding.
    
    Specified by:
    
    keySet in interface Map<K,V>
    
    Overrides:
    
    keySet in class AbstractMap<K,V>
    
    Returns:
    a set of the keys.
  - values
```
public Collection<V> values()
```
    Returns a collection of the values contained in this map. The collection is backed by this map so changes to one are reflected by the other. The collection supports remove, removeAll, retainAll and clear operations, and it does not support add or addAll operations.
    This method returns a collection which is the subclass of AbstractCollection. The iterator method of this subclass returns a "wrapper object" over the iterator of map's entrySet(). The size method wraps the map's size method and the contains method wraps the map's containsValue method.
    The collection is created when this method is called at first time and returned in response to all subsequent calls. This method may return different Collection when multiple calls to this method, since it has no synchronization performed.
    
    Specified by:
    
    values in interface Map<K,V>
    
    Overrides:
    
    values in class AbstractMap<K,V>
    
    Returns:
    a collection of the values contained in this map.
  - get
```
public V get(Object key)
```
    Returns the value of the mapping with the specified key.
    
    Specified by:
    
    get in interface Map<K,V>
    
    Overrides:
    
    get in class AbstractMap<K,V>
    
    Parameters:
    key - the key.
    
    Returns:
    the value of the mapping with the specified key, or null if no mapping for the specified key is found.
  - containsValue
```
public boolean containsValue(Object value)
```
    Returns whether this map contains the specified value.
    
    Specified by:
    
    containsValue in interface Map<K,V>
    
    Overrides:
    
    containsValue in class AbstractMap<K,V>
    
    Parameters:
    value - the value to search for.
    
    Returns:
    true if this map contains the specified value, false otherwise.
  - isEmpty
```
public boolean isEmpty()
```
    Returns the number of elements in this map.
    
    Specified by:
    
    isEmpty in interface Map<K,V>
    
    Overrides:
    
    isEmpty in class AbstractMap<K,V>
    
    Returns:
    the number of elements in this map.
    See Also:
    Map.size()
  - put
```
public V put(K key,
    V value)
```
    Maps the specified key to the specified value.
    
    Specified by:
    
    put in interface Map<K,V>
    
    Overrides:
    
    put in class AbstractMap<K,V>
    
    Parameters:
    key - the key.
    value - the value.
    
    Returns:
    the value of any previous mapping with the specified key or null if there was no mapping.
  - putAll
```
public void putAll(Map<? extends K,? extends V> map)
```
    Copies all the mappings in the given map to this map. These mappings will replace all mappings that this map had for any of the keys currently in the given map.
    
    Specified by:
    
    putAll in interface Map<K,V>
    
    Overrides:
    
    putAll in class AbstractMap<K,V>
    
    Parameters:
    map - the map to copy mappings from.
    
    Throws:
    
    NullPointerException - if map is null.
  - remove
```
public V remove(Object key)
```
    Removes the mapping with the specified key from this map.
    
    Specified by:
    
    remove in interface Map<K,V>
    
    Overrides:
    
    remove in class AbstractMap<K,V>
    
    Parameters:
    key - the key of the mapping to remove.
    
    Returns:
    the value of the removed mapping or null if no mapping for the specified key was found.
  - size
```
public int size()
```
    Returns the number of elements in this map.
    
    Specified by:
    
    size in interface Map<K,V>
    
    Overrides:
    
    size in class AbstractMap<K,V>
    
    Returns:
    the number of elements in this map.

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IT. Expert System.

Android Reference

WeakHashMap

Class WeakHashMap<K,V>

Nested Class Summary

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

Constructor Summary

Method Summary

Methods inherited from class java.util.AbstractMap

Methods inherited from class java.lang.Object

Methods inherited from interface java.util.Map

Constructor Detail

WeakHashMap

WeakHashMap

WeakHashMap

WeakHashMap

Method Detail

clear

containsKey

entrySet

keySet

values

get

containsValue

isEmpty

put

putAll

remove

size

Android Reference

Java basics

Java Enterprise Edition (EE)

Java Standard Edition (SE)

SQL

HTML

PHP

CSS

Java Script

MYSQL

JQUERY

VBS

REGEX

C

C++

C#

Design patterns

RFC (standard status)

RFC (proposed standard status)

RFC (draft standard status)

RFC (informational status)

RFC (experimental status)

RFC (best current practice status)

RFC (historic status)

RFC (unknown status)

IT dictionary