edu.rice.cs.cunit.util
Class SoftHashMap<K,V>

java.lang.Object
  edu.rice.cs.cunit.util.SoftHashMap<K,V>

All Implemented Interfaces:

java.util.Map<K,V>

public class SoftHashMap<K,V>
extends java.lang.Object
implements java.util.Map<K,V>

A hash map with soft references.

Author:

Mathias Ricken

Nested Class Summary

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

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

Field Summary

private java.util.HashMap<K,java.lang.ref.SoftReference<V>>	_map The wrapped map.
(package private) static int	DEFAULT_INITIAL_CAPACITY The default initial capacity - MUST be a power of two.
(package private) static float	DEFAULT_LOAD_FACTOR The load factor used when none specified in constructor.
(package private) static int	MAXIMUM_CAPACITY The maximum capacity, used if a higher value is implicitly specified by either of the constructors with arguments.

Constructor Summary

SoftHashMap()
Constructs an empty SoftHashMap with the default initial capacity (16) and the default load factor (0.75).

SoftHashMap(int initialCapacity)
Constructs an empty SoftHashMap with the specified initial capacity and the default load factor (0.75).

SoftHashMap(int initialCapacity, float loadFactor)
Constructs an empty SoftHashMap with the specified initial capacity and load factor.

SoftHashMap(java.util.Map<? extends K,? extends V> m)
Constructs a new SoftHashMap with the same mappings as the specified Map.

Method Summary

void	clear() Removes all mappings from this map (optional operation).
void	compact() Remove keys whose values have been removed.
boolean	containsKey(java.lang.Object key) Returns true if this map contains a mapping for the specified key.
boolean	containsValue(java.lang.Object value) Returns true if this map maps one or more keys to the specified value.
java.util.Set<java.util.Map.Entry<K,V>>	entrySet() Not supported.
V	get(java.lang.Object key) Returns the value to which this map maps the specified key.
boolean	isEmpty() Returns true if this map contains no key-value mappings.
java.util.Set<K>	keySet() Returns a set view of the keys contained in this map.
V	put(K k, V v) Associates the specified value with the specified key in this map (optional operation).
void	putAll(java.util.Map<? extends K,? extends V> map) Copies all of the mappings from the specified map to this map (optional operation).
V	remove(java.lang.Object key) Removes the mapping for this key from this map if it is present (optional operation).
int	size() Returns the number of key-value mappings in this map.
java.util.Collection<V>	values() Not supported.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface java.util.Map

equals, hashCode

Field Detail

_map

private java.util.HashMap<K,java.lang.ref.SoftReference<V>> _map

The wrapped map.

DEFAULT_INITIAL_CAPACITY

static final int DEFAULT_INITIAL_CAPACITY

The default initial capacity - MUST be a power of two.

See Also:

Constant Field Values

MAXIMUM_CAPACITY

static final int MAXIMUM_CAPACITY

The maximum capacity, used if a higher value is implicitly specified by either of the constructors with arguments. MUST be a power of two <= 1<<30.

See Also:

Constant Field Values

DEFAULT_LOAD_FACTOR

static final float DEFAULT_LOAD_FACTOR

The load factor used when none specified in constructor.

See Also:

Constant Field Values

Constructor Detail

SoftHashMap

public SoftHashMap(int initialCapacity,
                   float loadFactor)

Constructs an empty SoftHashMap with the specified initial capacity and load factor.

Parameters:

initialCapacity - The initial capacity.

loadFactor - The load factor.

Throws:

java.lang.IllegalArgumentException - if the initial capacity is negative or the load factor is nonpositive.

SoftHashMap

public SoftHashMap(int initialCapacity)

Constructs an empty SoftHashMap with the specified initial capacity and the default load factor (0.75).

Parameters:

initialCapacity - the initial capacity.

Throws:

java.lang.IllegalArgumentException - if the initial capacity is negative.

SoftHashMap

public SoftHashMap()

Constructs an empty SoftHashMap with the default initial capacity (16) and the default load factor (0.75).

SoftHashMap

public SoftHashMap(java.util.Map<? extends K,? extends V> m)

Constructs a new SoftHashMap with the same mappings as the specified Map. The SoftHashMap is created with default load factor (0.75) and an initial capacity sufficient to hold the mappings in the specified Map.

Parameters:

m - the map whose mappings are to be placed in this map.

Throws:

java.lang.NullPointerException - if the specified map is null.

Method Detail

get

public V get(java.lang.Object key)

Returns the value to which this map maps the specified key. Returns null if the map contains no mapping for this key. A return value of null does not necessarily indicate that the map contains no mapping for the key; it's also possible that the map explicitly maps the key to null. The containsKey operation may be used to distinguish these two cases.

Specified by:

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

Parameters:

key - key whose associated value is to be returned.

Returns:

the value to which this map maps the specified key.

Throws:

java.lang.NullPointerException - if the key is null and this map does not permit null keys.

See Also:

containsKey(Object)

compact

public void compact()

Remove keys whose values have been removed.

size

public int size()

Returns the number of key-value mappings in this map. If the map contains more than Integer.MAX_VALUE elements, returns Integer.MAX_VALUE.

This implementation returns entrySet().size().

Specified by:

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

Returns:

the number of key-value mappings in this map.

isEmpty

public boolean isEmpty()

Returns true if this map contains no key-value mappings.

Specified by:

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

Returns:

true if this map contains no key-value mappings.

containsKey

public boolean containsKey(java.lang.Object key)

Returns true if this map contains a mapping for the specified key. More formally, returns true if and only if this map contains a mapping for a key k such that (key==null ? k==null : key.equals(k)). (There can be at most one such mapping.)

Specified by:

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

Parameters:

key - key whose presence in this map is to be tested.

Returns:

true if this map contains a mapping for the specified key.

Throws:

java.lang.ClassCastException - if the key is of an inappropriate type for this map (optional).

java.lang.NullPointerException - if the key is null and this map does not permit null keys (optional).

containsValue

public boolean containsValue(java.lang.Object value)

Returns true if this map maps one or more keys to the specified value. More formally, returns true if and only if this map contains at least one mapping to a value v such that (value==null ? v==null : value.equals(v)). This operation will probably require time linear in the map size for most implementations of the Map interface.

Specified by:

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

Parameters:

value - value whose presence in this map is to be tested.

Returns:

true if this map maps one or more keys to the specified value.

Throws:

java.lang.ClassCastException - if the value is of an inappropriate type for this map (optional).

java.lang.NullPointerException - if the value is null and this map does not permit null values (optional).

put

public V put(K k,
             V v)

Associates the specified value with the specified key in this map (optional operation). If the map previously contained a mapping for this key, the old value is replaced by the specified value. (A map m is said to contain a mapping for a key k if and only if m.containsKey(k) would return true.))

Specified by:

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

Parameters:

k - key with which the specified value is to be associated.

v - value to be associated with the specified key.

Returns:

previous value associated with specified key, or null if there was no mapping for key. A null return can also indicate that the map previously associated null with the specified key, if the implementation supports null values.

Throws:

java.lang.UnsupportedOperationException - if the put operation is not supported by this map.

java.lang.ClassCastException - if the class of the specified key or value prevents it from being stored in this map.

java.lang.IllegalArgumentException - if some aspect of this key or value prevents it from being stored in this map.

java.lang.NullPointerException - if this map does not permit null keys or values, and the specified key or value is null.

remove

public V remove(java.lang.Object key)

Removes the mapping for this key from this map if it is present (optional operation). More formally, if this map contains a mapping from key k to value v such that (key==null ? k==null : key.equals(k)), that mapping is removed. (The map can contain at most one such mapping.)

Returns the value to which the map previously associated the key, or null if the map contained no mapping for this key. (A null return can also indicate that the map previously associated null with the specified key if the implementation supports null values.) The map will not contain a mapping for the specified key once the call returns.

Specified by:

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

Parameters:

key - key whose mapping is to be removed from the map.

Returns:

previous value associated with specified key, or null if there was no mapping for key.

Throws:

java.lang.ClassCastException - if the key is of an inappropriate type for this map (optional).

java.lang.NullPointerException - if the key is null and this map does not permit null keys (optional).

java.lang.UnsupportedOperationException - if the remove method is not supported by this map.

putAll

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

Copies all of the mappings from the specified map to this map (optional operation). The effect of this call is equivalent to that of calling put(k, v) on this map once for each mapping from key k to value v in the specified map. The behavior of this operation is unspecified if the specified map is modified while the operation is in progress.

Specified by:

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

Parameters:

map - Mappings to be stored in this map.

Throws:

java.lang.UnsupportedOperationException - if the putAll method is not supported by this map.

java.lang.ClassCastException - if the class of a key or value in the specified map prevents it from being stored in this map.

java.lang.IllegalArgumentException - some aspect of a key or value in the specified map prevents it from being stored in this map.

java.lang.NullPointerException - if the specified map is null, or if this map does not permit null keys or values, and the specified map contains null keys or values.

clear

public void clear()

Removes all mappings from this map (optional operation).

Specified by:

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

Throws:

java.lang.UnsupportedOperationException - clear is not supported by this map.

keySet

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

Returns a set view of the keys contained in this map. The set is backed by the map, so changes to the map are reflected in the set, and vice-versa. If the map is modified while an iteration over the set is in progress (except through the iterator's own remove operation), the results of the iteration are undefined. The set supports element removal, which removes the corresponding mapping from the map, via the Iterator.remove, Set.remove, removeAll retainAll, and clear operations. It does not support the add or addAll operations.

Specified by:

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

Returns:

a set view of the keys contained in this map.

values

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

Not supported.

Specified by:

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

Throws:

java.lang.UnsupportedOperationException

entrySet

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

Not supported.

Specified by:

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

Throws:

java.lang.UnsupportedOperationException