//-----------------------------------------------------------------------
/**
* Factory method to create a defaulting map.
* <p>
* The value specified is returned when a missing key is found.
*
* @param map the map to decorate, must not be null
* @param defaultValue the default value to return when the key is not found
* @throws IllegalArgumentException if map is null
*/
public static java.util.Map <Object, Object> decorate(java.util.Map <Object, Object> map, Object defaultValue)
{
if (defaultValue is Transformer)
{
defaultValue = ConstantTransformer.getInstance(defaultValue);
}
return(new DefaultedMap(map, defaultValue));
}
//-----------------------------------------------------------------------
/**
* Constructs a new empty <code>DefaultedMap</code> that decorates
* a <code>HashMap</code>.
* <p>
* The object passed in will be returned by the map whenever an
* unknown key is requested.
*
* @param defaultValue the default value to return when the key is not found
*/
public DefaultedMap(Object defaultValue)
: base(new java.util.HashMap <Object, Object>())
{
if (defaultValue is Transformer)
{
defaultValue = ConstantTransformer.getInstance(defaultValue);
}
this.value = defaultValue;
}
/**
* Creates a Transformer that will return the same object each time the
* transformer is used.
*
* @see org.apache.commons.collections.functors.ConstantTransformer
*
* @param constantToReturn the constant object to return each time in the transformer
* @return the transformer.
*/
public static Transformer constantTransformer(Object constantToReturn)
{
return(ConstantTransformer.getInstance(constantToReturn));
}
