org.apache.commons.collections.functors
Class ConstantTransformer

java.lang.Object
  |
  +--org.apache.commons.collections.functors.ConstantTransformer
All Implemented Interfaces:
Serializable, Transformer

public class ConstantTransformer
extends Object
implements Transformer, Serializable

Transformer implementation that returns the same constant each time.

No check is made that the object is immutable. In general, only immutable objects should use the constant factory. Mutable objects should use the prototype factory.

Since:
Commons Collections 3.0
Version:
$Revision: 1.2 $ $Date: 2004/01/14 21:43:09 $
Author:
Stephen Colebourne
See Also:
Serialized Form

Field Summary
static Transformer NULL_INSTANCE
          Returns null each time
 
Constructor Summary
ConstantTransformer(Object constantToReturn)
          Constructor that performs no validation.
 
Method Summary
static Transformer getInstance(Object constantToReturn)
          Transformer method that performs validation.
 Object transform(Object input)
          Always return constant.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

NULL_INSTANCE

public static final Transformer NULL_INSTANCE
Returns null each time
Constructor Detail

ConstantTransformer

public ConstantTransformer(Object constantToReturn)
Constructor that performs no validation. Use getInstance if you want that.
Parameters:
constantToReturn - the constant to return each time
Method Detail

getInstance

public static Transformer getInstance(Object constantToReturn)
Transformer method that performs validation.
Parameters:
constantToReturn - the constant object to return each time in the factory
Returns:
the constant factory.

transform

public Object transform(Object input)
Always return constant.
Specified by:
transform in interface Transformer
Following copied from interface: org.apache.commons.collections.Transformer
Parameters:
input - the object to be transformed
Returns:
a transformed object
Throws:
ClassCastException - (runtime) if the input is the wrong class
IllegalArgumentException - (runtime) if the input is invalid
FunctorException - (runtime) if the transform cannot be completed


Copyright © 2001-2004 Apache Software Foundation. All Rights Reserved.