Package org.apache.commons.collections4

# Interface Transformer<T,R>

Type Parameters:
  `T` - The type of the input to the function.
  `R` - The type of the result of the function.

All Superinterfaces:
  `Function<T,R>`

All Known Implementing Classes:
  `ChainedTransformer`, `CloneTransformer`, `ClosureTransformer`, `ConstantTransformer`, `ExceptionTransformer`, `FactoryTransformer`, `IfTransformer`, `InstantiateTransformer`, `InvokerTransformer`, `MapTransformer`, `NOPTransformer`, `PredicateTransformer`, `StringValueTransformer`, `SwitchTransformer`

Functional Interface:
  This is a functional interface and can therefore be used as the assignment target for a lambda expression or method reference.

@FunctionalInterface public interface Transformer<T,R> extends Function<T,R>
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 This will be deprecated in 5.0 in favor of `Function`.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `default R`
  `apply(T t)`
  `R`
  `transform(T input)`
  Transforms the input object into some output object.

  ### Methods inherited from interface java.util.function.Function

  `andThen, compose`

- ## Method Details

  - ### apply

    default R apply(T t)
    Specified by:
      `apply` in interface `Function<T,R>`

  - ### transform

    R transform(T input)
    Transforms the input object into some output object.

    The input object SHOULD be left unchanged.

    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.