This
abstract class is a partial implementation of the
Map interface that makes it easy to define simple
custom Map implementations. To define an
unmodifiable map, subclass AbstractMap and
override the entrySet( ) method so that it returns
a set of Map.Entry objects. (Note that you must
also implement Map.Entry, of course.) The returned
set should not support add( ) or remove(
), and its iterator should not support remove(
). In order to define a modifiable Map,
you must additionally override the put( ) method
and provide support for the remove( ) method of
the iterator returned by enTRySet( ).iterator( ).
In addition, it is conventional that all Map
implementations define two constructors: one that accepts no
arguments and another that accepts a Map of
initial mappings.
AbstractMap defines all Map
methods in terms of its entrySet( ) and
put( ) methods and the remove(
) method of the entry set iterator. Note, however, that the
implementation is based on a linear search of the
Set returned by enTRySet( ) and
is not efficient when the Map contains more than a
handful of entries. Some subclasses may want to override additional
AbstractMap methods to improve performance.
HashMap and treeMap use
different algorithms are are substantially more efficient.
public abstract class
AbstractMap<K,V> implements Map<K,V> {
// Protected Constructors
protected
AbstractMap ( );
// Methods Implementing Map
public void
clear ( );
public boolean
containsKey (Object
key );
public boolean
containsValue (Object
value );
public abstract Set<Map.Entry<K,V>>
entrySet ( );
public boolean
equals (Object
o );
public V
get (Object
key );
public int
hashCode ( );
public boolean
isEmpty ( );
public Set<K>
keySet ( );
public V
put (K
key , V
value );
public void
putAll (Map<? extends K,? extends V>
t );
public V
remove (Object
key );
public int
size ( );
public Collection<V>
values ( );
// Public Methods Overriding Object
public String
toString ( );
// Protected Methods Overriding Object
1.4 protected Object
clone ( ) throws CloneNotSupportedException;
}
EnumMap, HashMap,
IdentityHashMap, TReeMap,
WeakHashMap,
java.util.concurrent.ConcurrentHashMap