Class DefaultedMap

Decorates another Map returning a default value if the map does not contain the requested key.

When the get(Object) method is called with a key that does not exist in the map, this map will return the default value specified in the constructor/factory. Only the get method is altered, so the Map.containsKey(Object) can be used to determine if a key really is in the map or not.

The defaulted value is not added to the map. Compare this behaviour with LazyMap, which does add the value to the map (via a Transformer).

For instance:

 Map map = new DefaultedMap("NULL");
 Object obj = map.get("Surname");
 // obj == "NULL"
 

After the above code is executed the map is still empty.

Note that DefaultedMap is not synchronized and is not thread-safe. If you wish to use this map from multiple threads concurrently, you must use appropriate synchronization. The simplest approach is to wrap this map using java.util.Collections.synchronizedMap(Map). This class may throw exceptions when accessed by concurrent threads without synchronization.

protected final Object value

protected DefaultedMap(Map map,
                       Object value)

public DefaultedMap(Object defaultValue)

public static Map decorate(Map map,
                           Object defaultValue)

public static Map decorate(Map map,
                           Factory factory)

public static Map decorate(Map map,
                           Transformer factory)

public Object get(Object key)