com.tangosol.util
Class AbstractKeyBasedMap

java.lang.Object
  com.tangosol.util.Base
      com.tangosol.util.AbstractKeyBasedMap

All Implemented Interfaces:

Map

Direct Known Subclasses:

AbstractKeySetBasedMap, CacheStoreMap.ReadWriteMap, SimpleOverflowMap, SimpleSerializationMap

public abstract class AbstractKeyBasedMap
extends Base
implements Map

AbstractKeyBasedMap is a base class for Map implementations. The primary difference between the AbstractMap abstract class and this abstract class is this: that AbstractMap requires a sub-class to provide an Entry Set implementation, while AbstractKeyBasedMap requires a read-only sub-class to implement only get() and iterateKeys(), and a read-write sub-class to additionally implement only put() and remove().

Read-only implementations must implement iterateKeys() and get(Object). Read/write implementations must additionally implement put(Object, Object) and remove(Object). A number of the methods have implementations provided, but are extremely inefficient for Maps that contain large amounts of data, including clear(), containsKey(Object), size() (and by extension isEmpty()). Furthermore, if any of a number of method implementations has any cost of returning an "old value", such as is done by the put(java.lang.Object, java.lang.Object) and remove(Object) methods, then the putAll(java.util.Map) and removeBlind(Object) methods should also be implemented.

Author:

2005.07.13 cp

Nested Class Summary

class	AbstractKeyBasedMap.EntrySet A set of entries backed by this map.
protected class	AbstractKeyBasedMap.KeySet A set of keys backed by this map.
protected class	AbstractKeyBasedMap.ValuesCollection A Collection of values backed by this map.

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

Map.Entry

Constructor Summary

AbstractKeyBasedMap()

Method Summary

void	clear() Clear all key/value mappings.
protected Object	clone() Returns a shallow copy of this AbstractKeyBasedMap instance; the keySet, entrySet and values collections are not cloned or copied to (shared by) the clone.
boolean	containsKey(Object oKey) Returns true if this map contains a mapping for the specified key.
boolean	containsValue(Object oValue) Returns true if this Map maps one or more keys to the specified value.
Set	entrySet() Returns a set view of the mappings contained in this map.
boolean	equals(Object o) Compares the specified object with this map for equality.
abstract Object	get(Object oKey) Returns the value to which this map maps the specified key.
Map	getAll(Collection colKeys) Get all the specified keys, if they are in the Map.
int	hashCode() Returns the hash code value for this Map.
protected Set	instantiateEntrySet() Factory pattern: Create a Set that represents the entries in the Map.
protected Set	instantiateKeySet() Factory pattern: Create a Set that represents the keys in the Map
protected Collection	instantiateValues() Factory pattern: Instantiate the values Collection.
boolean	isEmpty() Returns true if this map contains no key-value mappings.
protected abstract Iterator	iterateKeys() Create an iterator over the keys in this Map.
Set	keySet() Returns a set view of the keys contained in this map.
Object	put(Object oKey, Object oValue) Associates the specified value with the specified key in this map.
void	putAll(Map map) Copies all of the mappings from the specified map to this map.
Object	remove(Object oKey) Removes the mapping for this key from this map if present.
protected boolean	removeBlind(Object oKey) Removes the mapping for this key from this map if present.
int	size() Returns the number of key-value mappings in this map.
String	toString() Returns a string representation of this Map.
Collection	values() Returns a collection view of the values contained in this map.

Constructor Detail

AbstractKeyBasedMap

public AbstractKeyBasedMap()

Method Detail

clear

public void clear()

Clear all key/value mappings.

Specified by:

clear in interface Map

containsKey

public boolean containsKey(Object oKey)

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

Specified by:

containsKey in interface Map

Returns:

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

containsValue

public boolean containsValue(Object oValue)

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

Specified by:

containsValue in interface Map

Returns:

true if this Map maps one or more keys to the specified value, false otherwise

entrySet

public Set entrySet()

Returns a set view of the mappings contained in this map. Each element in the returned set is an AbstractKeyBasedMap.EntrySet.Entry. 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 by the iterator's own remove operation, or by the setValue operation on a map entry returned by the iterator) 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 is not expected to support the add or addAll operations.

Specified by:

entrySet in interface Map

Returns:

a set view of the mappings contained in this map

get

public abstract Object get(Object oKey)

Returns the value to which this map maps the specified key.

Specified by:

get in interface Map

Parameters:

oKey - the key object

Returns:

the value to which this map maps the specified key, or null if the map contains no mapping for this key

isEmpty

public boolean isEmpty()

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

Specified by:

isEmpty in interface Map

Returns:

true if this map contains no key-value mappings

keySet

public 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. 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 is not expected to support the add or addAll operations.

Specified by:

keySet in interface Map

Returns:

a set view of the keys contained in this map

put

public Object put(Object oKey,
                  Object oValue)

Associates the specified value with the specified key in this map.

Specified by:

put in interface Map

Parameters:

oKey - key with which the specified value is to be associated

oValue - value to be associated with the specified key

Returns:

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

putAll

public void putAll(Map map)

Copies all of the mappings from the specified map to this map. The effect of this call is equivalent to that of calling put(java.lang.Object, java.lang.Object) on this map once for each mapping in the passed map. The behavior of this operation is unspecified if the passed map is modified while the operation is in progress.

Specified by:

putAll in interface Map

Parameters:

map - the Map containing the key/value pairings to put into this Map

remove

public Object remove(Object oKey)

Removes the mapping for this key from this map if present. Expensive: updates both the underlying cache and the local cache.

Specified by:

remove in interface Map

Parameters:

oKey - 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, if the implementation supports null values.

size

public int size()

Returns the number of key-value mappings in this map.

Specified by:

size in interface Map

Returns:

the number of key-value mappings in this map

values

public 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. If the map is modified while an iteration over the collection is in progress (except through the iterator's own remove operation), the results of the iteration are undefined. 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 is not expected to support the add or addAll operations.

Specified by:

values in interface Map

Returns:

a Collection view of the values contained in this map

getAll

public Map getAll(Collection colKeys)

Get all the specified keys, if they are in the Map. For each key that is in the cache, that key and its corresponding value will be placed in the map that is returned by this method. The absence of a key in the returned map indicates that it was not in the cache, which may imply (for caches that can load behind the scenes) that the requested data could not be loaded.

Parameters:

colKeys - a collection of keys that may be in the named cache

Returns:

a Map of keys to values for the specified keys passed in colKeys

iterateKeys

protected abstract Iterator iterateKeys()

Create an iterator over the keys in this Map. The Iterator must support remove() if the Map supports removal.

Returns:

a new instance of an Iterator over the keys in this Map

removeBlind

protected boolean removeBlind(Object oKey)

Removes the mapping for this key from this map if present. This method exists to allow sub-classes to optmiize remove functionalitly for situations in which the original value is not required.

Parameters:

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

Returns:

true iff the Map changed as the result of this operation

equals

public boolean equals(Object o)

Compares the specified object with this map for equality. Returns true if the given object is also a map and the two maps represent the same mappings. More formally, two maps t1 and t2 represent the same mappings if t1.keySet().equals(t2.keySet()) and for every key k in t1.keySet(), (t1.get(k)==null ? t2.get(k)==null : t1.get(k).equals(t2.get(k))) . This ensures that the equals method works properly across different implementations of the map interface.

Specified by:

equals in interface Map

Parameters:

o - object to be compared for equality with this Map

Returns:

true if the specified object is equal to this Map

hashCode

public int hashCode()

Returns the hash code value for this Map. The hash code of a Map is defined to be the sum of the hash codes of each entry in the Map's entrySet() view. This ensures that t1.equals(t2) implies that t1.hashCode()==t2.hashCode() for any two maps t1 and t2, as required by the general contract of Object.hashCode.

Specified by:

hashCode in interface Map

Returns:

the hash code value for this Map

toString

public String toString()

Returns a string representation of this Map. The string representation consists of a list of key-value mappings in the order returned by the Map's entrySet view's iterator, enclosed in braces ("{}"). Adjacent mappings are separated by the characters ", " (comma and space). Each key-value mapping is rendered as the key followed by an equals sign ("=") followed by the associated value. Keys and values are converted to strings as by String.valueOf(Object).

Returns:

a String representation of this Map

clone

protected Object clone()
                throws CloneNotSupportedException

Returns a shallow copy of this AbstractKeyBasedMap instance; the keySet, entrySet and values collections are not cloned or copied to (shared by) the clone.

Returns:

a shallow copy of this map

Throws:

CloneNotSupportedException

instantiateKeySet

protected Set instantiateKeySet()

Factory pattern: Create a Set that represents the keys in the Map

Returns:

a new instance of Set that represents the keys in the Map

instantiateEntrySet

protected Set instantiateEntrySet()

Factory pattern: Create a Set that represents the entries in the Map.

Returns:

a new instance of Set that represents the entries in the Map

instantiateValues

protected Collection instantiateValues()

Factory pattern: Instantiate the values Collection.

Returns:

a new instance of Collection that represents this Map's values