AbstractReferenceMap ("The Adobe AEM Quickstart and Web Application.")

java.lang.Object
- java.util.AbstractMap<K,V>
- - org.apache.commons.collections4.map.AbstractHashedMap<K,V>
  - - org.apache.commons.collections4.map.AbstractReferenceMap<K,V>

All Implemented Interfaces:

java.util.Map<K,V>, Get<K,V>, IterableGet<K,V>, IterableMap<K,V>, Put<K,V>

Direct Known Subclasses:

ReferenceIdentityMap, ReferenceMap
```
public abstract class AbstractReferenceMap<K,V>
extends AbstractHashedMap<K,V>
```
An abstract implementation of a hash-based map that allows the entries to be removed by the garbage collector.
This class implements all the features necessary for a subclass reference hash-based map. Key-value entries are stored in instances of the ReferenceEntry class which can be overridden and replaced. The iterators can similarly be replaced, without the need to replace the KeySet, EntrySet and Values view classes.
Overridable methods are provided to change the default hashing behaviour, and to change how entries are added to and removed from the map. Hopefully, all you need for unusual subclasses is here.
When you construct an AbstractReferenceMap, you can specify what kind of references are used to store the map's keys and values. If non-hard references are used, then the garbage collector can remove mappings if a key or value becomes unreachable, or if the JVM's memory is running low. For information on how the different reference types behave, see Reference.
Different types of references can be specified for keys and values. The keys can be configured to be weak but the values hard, in which case this class will behave like a WeakHashMap. However, you can also specify hard keys and weak values, or any other combination. The default constructor uses hard keys and soft values, providing a memory-sensitive cache.
This Map implementation does not allow null elements. Attempting to add a null key or value to the map will raise a NullPointerException.
All the available iterators can be reset back to the start by casting to ResettableIterator and calling reset().
This implementation is not synchronized. You can use Collections.synchronizedMap(java.util.Map<K, V>) to provide synchronized access to a ReferenceMap.

Since:

3.1 (extracted from ReferenceMap in 3.0)

See Also:

Reference

Nested Class Summary

Nested Classes
Modifier and Type Class and Description

static class AbstractReferenceMap.ReferenceStrength
Reference type enum.
- 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>

Nested Classes
Modifier and Type	Class and Description
`static class`	`AbstractReferenceMap.ReferenceStrength` Reference type enum.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`void`	`clear()` Clears this map.
`boolean`	`containsKey(java.lang.Object key)` Checks whether the map contains the specified key.
`boolean`	`containsValue(java.lang.Object value)` Checks whether the map contains the specified value.
`java.util.Set<java.util.Map.Entry<K,V>>`	`entrySet()` Returns a set view of this map's entries.
`V`	`get(java.lang.Object key)` Gets the value mapped to the key specified.
`boolean`	`isEmpty()` Checks whether the map is currently empty.
`java.util.Set<K>`	`keySet()` Returns a set view of this map's keys.
`MapIterator<K,V>`	`mapIterator()` Gets a MapIterator over the reference map.
`V`	`put(K key, V value)` Puts a key-value mapping into this map.
`V`	`remove(java.lang.Object key)` Removes the specified mapping from this map.
`int`	`size()` Gets the size of the map.
`java.util.Collection<V>`	`values()` Returns a collection view of this map's values.

Methods inherited from class org.apache.commons.collections4.map.AbstractHashedMap
equals, hashCode, putAll, toString

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

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

- Method Detail
  - size
```
public int size()
```
    Gets the size of the map.
    
    Specified by:
    
    size in interface java.util.Map<K,V>
    
    Specified by:
    
    size in interface Get<K,V>
    
    Overrides:
    
    size in class AbstractHashedMap<K,V>
    
    Returns:
    
    the size
    
    See Also:
    
    Map.size()
  - isEmpty
```
public boolean isEmpty()
```
    Checks whether the map is currently empty.
    
    Specified by:
    
    isEmpty in interface java.util.Map<K,V>
    
    Specified by:
    
    isEmpty in interface Get<K,V>
    
    Overrides:
    
    isEmpty in class AbstractHashedMap<K,V>
    
    Returns:
    
    true if the map is currently size zero
    
    See Also:
    
    Map.isEmpty()
  - containsKey
```
public boolean containsKey(java.lang.Object key)
```
    Checks whether the map contains the specified key.
    
    Specified by:
    
    containsKey in interface java.util.Map<K,V>
    
    Specified by:
    
    containsKey in interface Get<K,V>
    
    Overrides:
    
    containsKey in class AbstractHashedMap<K,V>
    
    Parameters:
    
    key - the key to search for
    
    Returns:
    
    true if the map contains the key
    
    See Also:
    
    Map.containsKey(Object)
  - containsValue
```
public boolean containsValue(java.lang.Object value)
```
    Checks whether the map contains the specified value.
    
    Specified by:
    
    containsValue in interface java.util.Map<K,V>
    
    Specified by:
    
    containsValue in interface Get<K,V>
    
    Overrides:
    
    containsValue in class AbstractHashedMap<K,V>
    
    Parameters:
    
    value - the value to search for
    
    Returns:
    
    true if the map contains the value
    
    See Also:
    
    Map.containsValue(Object)
  - get
```
public V get(java.lang.Object key)
```
    Gets the value mapped to the key specified.
    
    Specified by:
    
    get in interface java.util.Map<K,V>
    
    Specified by:
    
    get in interface Get<K,V>
    
    Overrides:
    
    get in class AbstractHashedMap<K,V>
    
    Parameters:
    
    key - the key
    
    Returns:
    
    the mapped value, null if no match
    
    See Also:
    
    Map.get(Object)
  - put
```
public V put(K key,
             V value)
```
    Puts a key-value mapping into this map. Neither the key nor the value may be null.
    
    Specified by:
    
    put in interface java.util.Map<K,V>
    
    Specified by:
    
    put in interface Put<K,V>
    
    Overrides:
    
    put in class AbstractHashedMap<K,V>
    
    Parameters:
    
    key - the key to add, must not be null
    
    value - the value to add, must not be null
    
    Returns:
    
    the value previously mapped to this key, null if none
    
    Throws:
    
    java.lang.NullPointerException - if either the key or value is null
    
    See Also:
    
    Map.put(Object, Object)
  - remove
```
public V remove(java.lang.Object key)
```
    Removes the specified mapping from this map.
    
    Specified by:
    
    remove in interface java.util.Map<K,V>
    
    Specified by:
    
    remove in interface Get<K,V>
    
    Overrides:
    
    remove in class AbstractHashedMap<K,V>
    
    Parameters:
    
    key - the mapping to remove
    
    Returns:
    
    the value mapped to the removed key, null if key not in map
    
    See Also:
    
    Map.remove(Object)
  - clear
```
public void clear()
```
    Clears this map.
    
    Specified by:
    
    clear in interface java.util.Map<K,V>
    
    Specified by:
    
    clear in interface Put<K,V>
    
    Overrides:
    
    clear in class AbstractHashedMap<K,V>
    
    See Also:
    
    Map.clear()
  - mapIterator
```
public MapIterator<K,V> mapIterator()
```
    Gets a MapIterator over the reference map. The iterator only returns valid key/value pairs.
    
    Specified by:
    
    mapIterator in interface IterableGet<K,V>
    
    Overrides:
    
    mapIterator in class AbstractHashedMap<K,V>
    
    Returns:
    
    a map iterator
  - entrySet
```
public java.util.Set<java.util.Map.Entry<K,V>> entrySet()
```
    Returns a set view of this map's entries. An iterator returned entry is valid until next() is called again. The setValue() method on the toArray entries has no effect.
    
    Specified by:
    
    entrySet in interface java.util.Map<K,V>
    
    Specified by:
    
    entrySet in interface Get<K,V>
    
    Overrides:
    
    entrySet in class AbstractHashedMap<K,V>
    
    Returns:
    
    a set view of this map's entries
    
    See Also:
    
    Map.entrySet()
  - keySet
```
public java.util.Set<K> keySet()
```
    Returns a set view of this map's keys.
    
    Specified by:
    
    keySet in interface java.util.Map<K,V>
    
    Specified by:
    
    keySet in interface Get<K,V>
    
    Overrides:
    
    keySet in class AbstractHashedMap<K,V>
    
    Returns:
    
    a set view of this map's keys
    
    See Also:
    
    Map.keySet()
  - values
```
public java.util.Collection<V> values()
```
    Returns a collection view of this map's values.
    
    Specified by:
    
    values in interface java.util.Map<K,V>
    
    Specified by:
    
    values in interface Get<K,V>
    
    Overrides:
    
    values in class AbstractHashedMap<K,V>
    
    Returns:
    
    a set view of this map's values
    
    See Also:
    
    Map.values()

Class AbstractReferenceMap<K,V>

Nested Class Summary

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

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

Method Summary

Methods inherited from class org.apache.commons.collections4.map.AbstractHashedMap

Methods inherited from class java.lang.Object

Methods inherited from interface java.util.Map

Method Detail

size

isEmpty

containsKey

containsValue

get

put

remove

clear

mapIterator

entrySet

keySet

values