ReferenceMap (Apache Commons Collections 3.2.2 API)

java.lang.Object
- java.util.AbstractMap
- - org.apache.commons.collections.ReferenceMap

All Implemented Interfaces:

Map

Deprecated.
Moved to map subpackage. Due to be removed in v4.0.
```
public class ReferenceMap
extends AbstractMap
```
Hash-based Map implementation that allows mappings to be removed by the garbage collector.
When you construct a ReferenceMap, 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.
The algorithms used are basically the same as those in HashMap. In particular, you can specify a load factor and capacity to suit your needs. All optional Map operations are supported.
However, this Map implementation does not allow null elements. Attempting to add a null key or or a null value to the map will raise a NullPointerException.
As usual, this implementation is not synchronized. You can use Collections.synchronizedMap(java.util.Map) to provide synchronized access to a ReferenceMap.

Since:

Commons Collections 2.1

Version:

$Revision: 972404 $ $Date: 2008-04-10 14:33:15 +0200 (Thu, 10 Apr 2008) $

Author:

Paul Jack

See Also:
Reference

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

Field Summary

Fields
Modifier and Type	Field and Description
`static int`	`HARD` Deprecated. Constant indicating that hard references should be used.
`static int`	`SOFT` Deprecated. Constant indicating that soft references should be used.
`static int`	`WEAK` Deprecated. Constant indicating that weak references should be used.

Constructor Summary

Constructors
Constructor and Description
`ReferenceMap()` Deprecated. Constructs a new `ReferenceMap` that will use hard references to keys and soft references to values.
`ReferenceMap(int keyType, int valueType)` Deprecated. Constructs a new `ReferenceMap` that will use the specified types of references.
`ReferenceMap(int keyType, int valueType, boolean purgeValues)` Deprecated. Constructs a new `ReferenceMap` that will use the specified types of references.
`ReferenceMap(int keyType, int valueType, int capacity, float loadFactor)` Deprecated. Constructs a new `ReferenceMap` with the specified reference types, load factor and initial capacity.
`ReferenceMap(int keyType, int valueType, int capacity, float loadFactor, boolean purgeValues)` Deprecated. Constructs a new `ReferenceMap` with the specified reference types, load factor and initial capacity.

Method Summary

Methods
Modifier and Type	Method and Description
`void`	`clear()` Deprecated. Clears this map.
`boolean`	`containsKey(Object key)` Deprecated. Returns `true` if this map contains the given key.
`Set`	`entrySet()` Deprecated. Returns a set view of this map's entries.
`Object`	`get(Object key)` Deprecated. Returns the value associated with the given key, if any.
`boolean`	`isEmpty()` Deprecated. Returns `true` if this map is empty.
`Set`	`keySet()` Deprecated. Returns a set view of this map's keys.
`Object`	`put(Object key, Object value)` Deprecated. Associates the given key with the given value.
`Object`	`remove(Object key)` Deprecated. Removes the key and its associated value from this map.
`int`	`size()` Deprecated. Returns the size of this map.
`Collection`	`values()` Deprecated. Returns a collection view of this map's values.

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

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

- Field Detail
  - HARD
```
public static final int HARD
```
    Deprecated.
    
    Constant indicating that hard references should be used.
    
    See Also:
    Constant Field Values
  - SOFT
```
public static final int SOFT
```
    Deprecated.
    
    Constant indicating that soft references should be used.
    
    See Also:
    Constant Field Values
  - WEAK
```
public static final int WEAK
```
    Deprecated.
    
    Constant indicating that weak references should be used.
    
    See Also:
    Constant Field Values
- Constructor Detail
  - ReferenceMap
```
public ReferenceMap()
```
    Deprecated.
    
    Constructs a new ReferenceMap that will use hard references to keys and soft references to values.
  - ReferenceMap
```
public ReferenceMap(int keyType,
            int valueType,
            boolean purgeValues)
```
    Deprecated.
    
    Constructs a new ReferenceMap that will use the specified types of references.
    
    Parameters:
    keyType - the type of reference to use for keys; must be HARD, SOFT, WEAK
    valueType - the type of reference to use for values; must be HARD, SOFT, WEAK
    purgeValues - should the value be automatically purged when the key is garbage collected
  - ReferenceMap
```
public ReferenceMap(int keyType,
            int valueType)
```
    Deprecated.
    
    Constructs a new ReferenceMap that will use the specified types of references.
    
    Parameters:
    keyType - the type of reference to use for keys; must be HARD, SOFT, WEAK
    valueType - the type of reference to use for values; must be HARD, SOFT, WEAK
  - ReferenceMap
```
public ReferenceMap(int keyType,
            int valueType,
            int capacity,
            float loadFactor,
            boolean purgeValues)
```
    Deprecated.
    
    Constructs a new ReferenceMap with the specified reference types, load factor and initial capacity.
    
    Parameters:
    keyType - the type of reference to use for keys; must be HARD, SOFT, WEAK
    valueType - the type of reference to use for values; must be HARD, SOFT, WEAK
    capacity - the initial capacity for the map
    loadFactor - the load factor for the map
    purgeValues - should the value be automatically purged when the key is garbage collected
  - ReferenceMap
```
public ReferenceMap(int keyType,
            int valueType,
            int capacity,
            float loadFactor)
```
    Deprecated.
    
    Constructs a new ReferenceMap with the specified reference types, load factor and initial capacity.
    
    Parameters:
    keyType - the type of reference to use for keys; must be HARD, SOFT, WEAK
    valueType - the type of reference to use for values; must be HARD, SOFT, WEAK
    capacity - the initial capacity for the map
    loadFactor - the load factor for the map
- Method Detail
  - size
```
public int size()
```
    Deprecated.
    
    Returns the size of this map.
    
    Specified by:
    
    size in interface Map
    
    Overrides:
    
    size in class AbstractMap
    
    Returns:
    the size of this map
  - isEmpty
```
public boolean isEmpty()
```
    Deprecated.
    
    Returns true if this map is empty.
    
    Specified by:
    
    isEmpty in interface Map
    
    Overrides:
    
    isEmpty in class AbstractMap
    
    Returns:
    true if this map is empty
  - containsKey
```
public boolean containsKey(Object key)
```
    Deprecated.
    
    Returns true if this map contains the given key.
    
    Specified by:
    
    containsKey in interface Map
    
    Overrides:
    
    containsKey in class AbstractMap
    
    Returns:
    true if the given key is in this map
  - get
```
public Object get(Object key)
```
    Deprecated.
    
    Returns the value associated with the given key, if any.
    
    Specified by:
    
    get in interface Map
    
    Overrides:
    
    get in class AbstractMap
    
    Returns:
    the value associated with the given key, or null if the key maps to no value
  - put
```
public Object put(Object key,
         Object value)
```
    Deprecated.
    
    Associates the given key with the given value.
    Neither the key nor the value may be null.
    
    Specified by:
    
    put in interface Map
    
    Overrides:
    
    put in class AbstractMap
    
    Parameters:
    key - the key of the mapping
    value - the value of the mapping
    
    Returns:
    the last value associated with that key, or null if no value was associated with the key
    
    Throws:
    
    NullPointerException - if either the key or value is null
  - remove
```
public Object remove(Object key)
```
    Deprecated.
    
    Removes the key and its associated value from this map.
    
    Specified by:
    
    remove in interface Map
    
    Overrides:
    
    remove in class AbstractMap
    
    Parameters:
    key - the key to remove
    
    Returns:
    the value associated with that key, or null if the key was not in the map
  - clear
```
public void clear()
```
    Deprecated.
    
    Clears this map.
    
    Specified by:
    
    clear in interface Map
    
    Overrides:
    
    clear in class AbstractMap
  - entrySet
```
public Set entrySet()
```
    Deprecated.
    
    Returns a set view of this map's entries.
    
    Specified by:
    
    entrySet in interface Map
    
    Specified by:
    
    entrySet in class AbstractMap
    
    Returns:
    a set view of this map's entries
  - keySet
```
public Set keySet()
```
    Deprecated.
    
    Returns a set view of this map's keys.
    
    Specified by:
    
    keySet in interface Map
    
    Overrides:
    
    keySet in class AbstractMap
    
    Returns:
    a set view of this map's keys
  - values
```
public Collection values()
```
    Deprecated.
    
    Returns a collection view of this map's values.
    
    Specified by:
    
    values in interface Map
    
    Overrides:
    
    values in class AbstractMap
    
    Returns:
    a collection view of this map's values.

Class ReferenceMap

Nested Class Summary

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

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.util.AbstractMap

Methods inherited from class java.lang.Object

Field Detail

HARD

SOFT

WEAK

Constructor Detail

ReferenceMap

ReferenceMap

ReferenceMap

ReferenceMap

ReferenceMap

Method Detail

size

isEmpty

containsKey

get

put

remove

clear

entrySet

keySet

values