WeakMap (LibreOffice types for the Java Uno typesystem)

java.lang.Object
- com.sun.star.lib.util.WeakMap<K,V>

All Implemented Interfaces:

Map
```
public final class WeakMap<K,V>
extends Object
implements Map
```
A hash map that holds values of type WeakReference.
Like HashMap, this implementation provides all of the optional map operations, and permits the null key.

Also like HashMap, this implementation is not synchronized. If multiple threads share an instance, and at least one of them executes any modifying operations on the WeakMap, they have to use external synchronization.

Unlike other map implementations, WeakMap is asymmetric in that put expects the given value to be a plain object that is then wrapped in a WeakReference, while the occurrences of values in all other methods (containsValue, entrySet, equals, get, hashCode, remove, values, and also the return value of put) expect already wrapped instances of WeakReference. That is, after weakMap.put("key", o), weakMap.get("key").equals(o) does not work as naïvely expected; neither does weakMap1.putAll(weakMap2).

At an arbitrary time after the WeakReference value of an entry has been cleared by the garbage collector, the entry is automatically removed from the map.

Values placed into a WeakMap may optionally support the DisposeNotifier interface. For those that do, the associated WeakReference wrappers are automatically cleared as soon as the values are disposed.
Note that this class does not actually implement the Map interface properly, the type of the return value of the entrySet and values methods is wrong, but the "implements Map" is retained for backward compatibility.

Constructor Summary

Constructors
Constructor and Description

WeakMap()
Constructs an empty WeakMap.

WeakMap(Map<K,V> m)
Constructs a new WeakMap with the same mappings as the specified Map.

Constructors
Constructor and Description
`WeakMap()` Constructs an empty `WeakMap`.
`WeakMap(Map<K,V> m)` Constructs a new `WeakMap` with the same mappings as the specified `Map`.

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`void`	`clear()` Removes all mappings from this map.
`boolean`	`containsKey(Object key)` Returns `true` if this map contains a mapping for the specified key.
`boolean`	`containsValue(Object value)` Returns `true` if this map maps one or more keys to the specified value.
`Set`	`entrySet()` Returns a collection view of the mappings contained in this map.
`boolean`	`equals(Object o)`
`WeakReference<V>`	`get(Object key)` Returns the value to which the specified key is mapped in this map, or `null` if the map contains no mapping for this key.
`static <T> T`	`getValue(Object ref)` Returns the referent of a `WeakReference`, silently handling a `null` argument.
`int`	`hashCode()`
`boolean`	`isEmpty()` Returns `true` if this map contains no key–value mappings.
`Set<K>`	`keySet()` Returns a view of the keys contained in this map.
`Object`	`put(Object key, Object value)` Associates the specified value with the specified key in this map.
`void`	`putAll(Map m)` Copies all of the mappings from the specified map to this map.
`Object`	`remove(Object key)` Removes the mapping for this key from this map if present.
`int`	`size()` Returns the number of key–value mappings in this map.
`Collection<WeakReference<V>>`	`values()` Returns a collection view of the values contained in this map.

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

Methods inherited from interface java.util.Map
compute, computeIfAbsent, computeIfPresent, forEach, getOrDefault, merge, putIfAbsent, remove, replace, replace, replaceAll

- Constructor Detail
  - WeakMap
```
public WeakMap()
```
    Constructs an empty WeakMap.
  - WeakMap
```
public WeakMap(Map<K,V> m)
```
    Constructs a new WeakMap with the same mappings as the specified Map.
    
    Parameters:
    
    m - the map whose mappings are to be placed in this map
- Method Detail
  - size
```
public int size()
```
    Returns the number of key–value mappings in this map.
    This is a non-modifying operation.
    
    Specified by:
    
    size in interface Map
    
    Returns:
    
    the number of key–value mappings in this map
  - isEmpty
```
public boolean isEmpty()
```
    Returns true if this map contains no key–value mappings.
    This is a non-modifying operation.
    
    Specified by:
    
    isEmpty in interface Map
    
    Returns:
    
    true if this map contains no key–value mappings
  - containsKey
```
public boolean containsKey(Object key)
```
    Returns true if this map contains a mapping for the specified key.
    This is a non-modifying operation.
    
    Specified by:
    
    containsKey in interface Map
    
    Parameters:
    
    key - the key whose presence in this map is to be tested
    
    Returns:
    
    true if this map contains a mapping for the specified key
  - containsValue
```
public boolean containsValue(Object value)
```
    Returns true if this map maps one or more keys to the specified value.
    This is a non-modifying operation.
    
    Specified by:
    
    containsValue in interface Map
    
    Parameters:
    
    value - the value whose presence in this map is to be tested
    
    Returns:
    
    true if this map maps one or more keys to the specified value
  - get
```
public WeakReference<V> get(Object key)
```
    Returns the value to which the specified key is mapped in this map, or null if the map contains no mapping for this key.
    This is a non-modifying operation.
    
    Specified by:
    
    get in interface Map
    
    Parameters:
    
    key - the key whose associated value is to be returned
    
    Returns:
    
    the value to which this map maps the specified key, or null if the map contains no mapping for this key
  - put
```
public Object put(Object key,
                  Object value)
```
    Associates the specified value with the specified key in this map.
    This is a modifying operation.
    
    Specified by:
    
    put in interface Map
    
    Parameters:
    
    key - the key with which the specified value is to be associated
    
    value - the value to be associated with the specified key. This must be a plain object, which is then wrapped in a WeakReference.
    
    Returns:
    
    previous value associated with the specified key, or null if there was no mapping for the key
  - remove
```
public Object remove(Object key)
```
    Removes the mapping for this key from this map if present.
    This is a modifying operation.
    
    Specified by:
    
    remove in interface Map
    
    Parameters:
    
    key - the key whose mapping is to be removed from the map
    
    Returns:
    
    previous value associated with the specified key, or null if there was no mapping for the key
  - putAll
```
public void putAll(Map m)
```
    Copies all of the mappings from the specified map to this map.
    This is a modifying operation.
    
    Specified by:
    
    putAll in interface Map
    
    Parameters:
    
    m - mappings to be stored in this map. The values of those mappings must be plain objects, which are then wrapped in instances of WeakReference.
  - clear
```
public void clear()
```
    Removes all mappings from this map.
    This is a modifying operation.
    
    Specified by:
    
    clear in interface Map
  - keySet
```
public Set<K> keySet()
```
    Returns a view of the keys contained in this map.
    This is a non-modifying operation.
    
    Specified by:
    
    keySet in interface Map
    
    Returns:
    
    a set view of the keys contained in this map
  - values
```
public Collection<WeakReference<V>> values()
```
    Returns a collection view of the values contained in this map.
    This is a non-modifying operation.
    
    Specified by:
    
    values in interface Map
    
    Returns:
    
    a collection view of the values contained in this map
  - entrySet
```
public Set entrySet()
```
    Returns a collection view of the mappings contained in this map.
    This is a non-modifying operation.
    
    Specified by:
    
    entrySet in interface Map
    
    Returns:
    
    a collection view of the mappings contained in this map
  - equals
```
public boolean equals(Object o)
```
    Specified by:
    
    equals in interface Map
    
    Overrides:
    
    equals in class Object
  - hashCode
```
public int hashCode()
```
    Specified by:
    
    hashCode in interface Map
    
    Overrides:
    
    hashCode in class Object
  - getValue
```
public static <T> T getValue(Object ref)
```
    Returns the referent of a WeakReference, silently handling a null argument.
    This static method is useful to wrap around the return values of methods like get.
    
    Parameters:
    
    ref - must be either an instance of WeakReference or null
    
    Returns:
    
    the referent of the specified WeakReference, or null if ref is null

Class WeakMap<K,V>

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Methods inherited from interface java.util.Map

Constructor Detail

WeakMap

WeakMap

Method Detail

size

isEmpty

containsKey

containsValue

get

put

remove

putAll

clear

keySet

values

entrySet

equals

hashCode

getValue