goodslib
Class PersistentHashMap

java.lang.Object
  extended bygoodsjpi.Persistent
      extended bygoodslib.PersistentAbstractMap
          extended bygoodslib.PersistentHashMap
All Implemented Interfaces:
java.lang.Cloneable, java.util.Map, java.io.Serializable

public class PersistentHashMap
extends PersistentAbstractMap
implements java.util.Map, java.lang.Cloneable

Hash table based implementation of the Map interface. This implementation provides all of the optional map operations, and permits null values and the null key. (The HashMap class is roughly equivalent to Hashtable, except that it is unsynchronized and permits nulls.) This class makes no guarantees as to the order of the map; in particular, it does not guarantee that the order will remain constant over time.

This implementation provides constant-time performance for the basic operations (get and put), assuming the hash function disperses the elements properly among the buckets. Iteration over collection views requires time proportional to the "capacity" of the HashMap instance (the number of buckets) plus its size (the number of key-value mappings). Thus, it's very important not to set the intial capacity too high (or the load factor too low) if iteration performance is important.

Note that this implementation is not synchronized. If multiple threads access this map concurrently, and at least one of the threads modifies the map structurally, it must be synchronized externally. (A structural modification is any operation that adds or deletes one or more mappings; merely changing the value associated with a key that an instance already contains is not a structural modification.) This is typically accomplished by synchronizing on some object that naturally encapsulates the map. If no such object exists, the map should be "wrapped" using the Collections.synchronizedMap method. This is best done at creation time, to prevent accidental unsynchronized access to the map:

 Map m = Collections.synchronizedMap(new HashMap(...));
 

The iterators returned by all of this class's "collection view methods" are fail-fast: if the map is structurally modified at any time after the iterator is created, in any way except through the iterator's own remove or add methods, the iterator will throw a ConcurrentModificationException. Thus, in the face of concurrent modification, the iterator fails quickly and cleanly, rather than risking arbitrary, non-deterministic behavior at an undetermined time in the future.

Since:
1.2
See Also:
Object.hashCode(), Collection, Map, TreeMap, Hashtable, Serialized Form

Field Summary
 
Fields inherited from class goodsjpi.Persistent
defaultMetaobject, metaobject
 
Constructor Summary
PersistentHashMap()
          Constructs a new, empty map with a default capacity and load factor, which is 0.75.
PersistentHashMap(int initialCapacity)
          Constructs a new, empty map with the specified initial capacity and default load factor, which is 0.75.
PersistentHashMap(int initialCapacity, float loadFactor)
          Constructs a new, empty map with the specified initial capacity and the specified load factor.
PersistentHashMap(java.util.Map t)
          Constructs a new map with the same mappings as the given map.
 
Method Summary
 void clear()
          Removes all mappings from this map.
 java.lang.Object clone()
          Returns a shallow copy of this PersistentHashMap instance: the keys and values themselves are not cloned.
 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 entrySet()
          Returns a collection view of the mappings contained in this map.
 java.lang.Object get(java.lang.Object key)
          Returns the value to which this map maps the specified key.
protected  goodslib.PersistentHashMap.Entry getEntry(java.lang.Object key)
           
 goodslib.PersistentHashMap.Entry getNext(goodslib.PersistentHashMap.HashIterator iterator)
           
 boolean isEmpty()
          Returns true if this map contains no key-value mappings.
 java.util.Set keySet()
          Returns a set view of the keys contained in this map.
 java.lang.Object put(java.lang.Object key, java.lang.Object value)
          Associates the specified value with the specified key in this map.
 void putAll(java.util.Map t)
          Copies all of the mappings from the specified map to this one.
 java.lang.Object remove(java.lang.Object key)
          Removes the mapping for this key from this map if present.
 void removeCurr(goodslib.PersistentHashMap.HashIterator iterator)
           
 int size()
          Returns the number of key-value mappings in this map.
 java.util.Collection values()
          Returns a collection view of the values contained in this map.
 
Methods inherited from class goodslib.PersistentAbstractMap
equals, hashCode, toString
 
Methods inherited from class goodsjpi.Persistent
attachToStorage, clusterWith, finalize, getDatabase, getOid, getStorageId, onLoad
 
Methods inherited from class java.lang.Object
getClass, notify, notifyAll, wait, wait, wait
 
Methods inherited from interface java.util.Map
equals, hashCode
 

Constructor Detail

PersistentHashMap

public PersistentHashMap(int initialCapacity,
                         float loadFactor)
Constructs a new, empty map with the specified initial capacity and the specified load factor.

Parameters:
initialCapacity - the initial capacity of the PersistentHashMap.
loadFactor - the load factor of the PersistentHashMap
Throws:
java.lang.IllegalArgumentException - if the initial capacity is less than zero, or if the load factor is nonpositive.

PersistentHashMap

public PersistentHashMap(int initialCapacity)
Constructs a new, empty map with the specified initial capacity and default load factor, which is 0.75.

Parameters:
initialCapacity - the initial capacity of the PersistentHashMap.
Throws:
java.lang.IllegalArgumentException - if the initial capacity is less than zero.

PersistentHashMap

public PersistentHashMap()
Constructs a new, empty map with a default capacity and load factor, which is 0.75.


PersistentHashMap

public PersistentHashMap(java.util.Map t)
Constructs a new map with the same mappings as the given map. The map is created with a capacity of twice the number of mappings in the given map or 11 (whichever is greater), and a default load factor, which is 0.75.

Parameters:
t - 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.

Specified by:
size in interface java.util.Map
Overrides:
size in class PersistentAbstractMap
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
Overrides:
isEmpty in class PersistentAbstractMap
Returns:
true if this map contains no key-value mappings.

containsValue

public boolean containsValue(java.lang.Object value)
Returns true if this map maps one or more keys to the specified value.

Specified by:
containsValue in interface java.util.Map
Overrides:
containsValue in class PersistentAbstractMap
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.

containsKey

public boolean containsKey(java.lang.Object key)
Returns true if this map contains a mapping for the specified key.

Specified by:
containsKey in interface java.util.Map
Overrides:
containsKey in class PersistentAbstractMap
Parameters:
key - key whose presence in this Map is to be tested.
Returns:
true if this map contains a mapping for the specified key.

getEntry

protected goodslib.PersistentHashMap.Entry getEntry(java.lang.Object key)

get

public java.lang.Object 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
Overrides:
get in class PersistentAbstractMap
Parameters:
key - key whose associated value is to be returned.
Returns:
the value to which this map maps the specified key.
See Also:
PersistentAbstractMap.containsKey(Object)

put

public java.lang.Object put(java.lang.Object key,
                            java.lang.Object value)
Associates the specified value with the specified key in this map. If the map previously contained a mapping for this key, the old value is replaced.

Specified by:
put in interface java.util.Map
Overrides:
put in class PersistentAbstractMap
Parameters:
key - key with which the specified value is to be associated.
value - 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 PersistentHashMap previously associated null with the specified key.

remove

public java.lang.Object remove(java.lang.Object key)
Removes the mapping for this key from this map if present.

Specified by:
remove in interface java.util.Map
Overrides:
remove in class PersistentAbstractMap
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. A null return can also indicate that the map previously associated null with the specified key.

putAll

public void putAll(java.util.Map t)
Copies all of the mappings from the specified map to this one. These mappings replace any mappings that this map had for any of the keys currently in the specified Map.

Specified by:
putAll in interface java.util.Map
Overrides:
putAll in class PersistentAbstractMap
Parameters:
t - Mappings to be stored in this map.

clear

public void clear()
Removes all mappings from this map.

Specified by:
clear in interface java.util.Map
Overrides:
clear in class PersistentAbstractMap

clone

public java.lang.Object clone()
Returns a shallow copy of this PersistentHashMap instance: the keys and values themselves are not cloned.

Overrides:
clone in class Persistent
Returns:
a shallow copy of this map.

getNext

public goodslib.PersistentHashMap.Entry getNext(goodslib.PersistentHashMap.HashIterator iterator)

removeCurr

public void removeCurr(goodslib.PersistentHashMap.HashIterator iterator)

keySet

public java.util.Set 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. The set supports element removal, which removes the corresponding mapping from this 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
Overrides:
keySet in class PersistentAbstractMap
Returns:
a set view of the keys contained in this map.

values

public java.util.Collection values()
Returns a collection view of the values contained in this map. The collection is backed by the map, so changes to the map are reflected in the collection, and vice-versa. The collection supports element removal, which removes the corresponding mapping from this map, via the Iterator.remove, Collection.remove, removeAll, retainAll, and clear operations. It does not support the add or addAll operations.

Specified by:
values in interface java.util.Map
Overrides:
values in class PersistentAbstractMap
Returns:
a collection view of the values contained in this map.

entrySet

public java.util.Set entrySet()
Returns a collection view of the mappings contained in this map. Each element in the returned collection is a Map.Entry. The collection is backed by the map, so changes to the map are reflected in the collection, and vice-versa. The collection supports element removal, which removes the corresponding mapping from the map, via the Iterator.remove, Collection.remove, removeAll, retainAll, and clear operations. It does not support the add or addAll operations.

Specified by:
entrySet in interface java.util.Map
Specified by:
entrySet in class PersistentAbstractMap
Returns:
a collection view of the mappings contained in this map.