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package org.apache.commons.collections4;

Defines a functor interface implemented by classes that transform one
object into another.

A Transformer converts the input object to the output object.
The input object should be left unchanged.
Transformers are typically used for type conversions, or extracting data
from an object.

 Standard implementations of common transformers are provided by TransformerUtils. These include method invocation, returning a constant, cloning and returning the string value. 
Type parameters:
<I> – the input type to the transformer
<O> – the output type from the transformer
Since:
1.0/**
 * Defines a functor interface implemented by classes that transform one
 * object into another.
 * <p>
 * A <code>Transformer</code> converts the input object to the output object.
 * The input object should be left unchanged.
 * Transformers are typically used for type conversions, or extracting data
 * from an object.
 * </p>
 * <p>
 * Standard implementations of common transformers are provided by
 * {@link TransformerUtils}. These include method invocation, returning a constant,
 * cloning and returning the string value.
 * </p>
 *
 * @param <I> the input type to the transformer
 * @param <O> the output type from the transformer
 *
 * @since 1.0
 */
@FunctionalInterface
public interface Transformer<I, O> {

    
Transforms the input object (leaving it unchanged) into some output object.
Params:
input –  the object to be transformed, should be left unchanged
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
Returns:
a transformed object/**
     * Transforms the input object (leaving it unchanged) into some output object.
     *
     * @param input  the object to be transformed, should be left unchanged
     * @return a transformed object
     * @throws ClassCastException (runtime) if the input is the wrong class
     * @throws IllegalArgumentException (runtime) if the input is invalid
     * @throws FunctorException (runtime) if the transform cannot be completed
     */
    O transform(I input);

}