org.apache.commons.collections4

## Interface Transformer<I,O>

- Type Parameters:
    `I` - the input type to the transformer
    `O` - the output type from the transformer
  All Known Implementing Classes:
    ChainedTransformer, CloneTransformer, ClosureTransformer, ConstantTransformer, ExceptionTransformer, FactoryTransformer, InstantiateTransformer, InvokerTransformer, MapTransformer, NOPTransformer, PredicateTransformer, StringValueTransformer, SwitchTransformer

      public interface Transformer<I,O>

  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.

  Since:
    1.0
  Version:
    $Id: Transformer.java 1543278 2013-11-19 00:54:07Z ggregory $

- - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `O` | `transform(I input)` Transforms the input object (leaving it unchanged) into some output object.

- - ### Method Detail

    - #### transform

          O transform(I input)

      Transforms the input object (leaving it unchanged) into some output object.
      Parameters:
        `input` - the object to be transformed, should be left unchanged
      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

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