# Class SwitchTransformer<T,R>

java.lang.Object
org.apache.commons.collections4.functors.SwitchTransformer<T,R>

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

All Implemented Interfaces:
  `Serializable`, `Function<T,R>`, `Transformer<T,R>`

public class SwitchTransformer<T,R> extends Object implements Transformer<T,R>, Serializable
Transformer implementation calls the transformer whose predicate returns true, like a switch statement.

Since:
  3.0
See Also:
  - Serialized Form

- ## Constructor Summary

  Constructors
  Constructor
  Description
  `SwitchTransformer(Predicate<? super T>[] predicates, Transformer<? super T,? extends R>[] transformers, Transformer<? super T,? extends R> defaultTransformer)`
  Constructor that performs no validation.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `Transformer<? super T,? extends R>`
  `getDefaultTransformer()`
  Gets the default transformer.
  `Predicate<? super T>[]`
  `getPredicates()`
  Gets the predicates.
  `Transformer<? super T,? extends R>[]`
  `getTransformers()`
  Gets the transformers.
  `static <I, O> Transformer<I,O>`
  `switchTransformer(Map<? extends Predicate<? super I>,? extends Transformer<? super I,? extends O>> map)`
  Create a new Transformer that calls one of the transformers depending on the predicates.
  `static <I, O> Transformer<I,O>`
  `switchTransformer(Predicate<? super I>[] predicates, Transformer<? super I,? extends O>[] transformers, Transformer<? super I,? extends O> defaultTransformer)`
  Factory method that performs validation and copies the parameter arrays.
  `R`
  `transform(T input)`
  Transforms the input to result by calling the transformer whose matching predicate returns true.

  ### Methods inherited from class java.lang.Object

  `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

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

  `andThen, compose`

  ### Methods inherited from interface org.apache.commons.collections4.Transformer

  `apply`

- ## Constructor Details

  - ### SwitchTransformer

    public SwitchTransformer(Predicate<? super T>[] predicates, Transformer<? super T,? extends R>[] transformers, Transformer<? super T,? extends R> defaultTransformer)
    Constructor that performs no validation. Use `switchTransformer` if you want that.
    Parameters:
      `predicates` - array of predicates, cloned, no nulls
      `transformers` - matching array of transformers, cloned, no nulls
      `defaultTransformer` - the transformer to use if no match, null means return null

- ## Method Details

  - ### switchTransformer

    public static <I, O> Transformer<I,O> switchTransformer(Map<? extends Predicate<? super I>,? extends Transformer<? super I,? extends O>> map)
    Create a new Transformer that calls one of the transformers depending on the predicates.

    The Map consists of Predicate keys and Transformer values. A transformer is called if its matching predicate returns true. Each predicate is evaluated until one returns true. If no predicates evaluate to true, the default transformer is called. The default transformer is set in the map with a null key. The ordering is that of the iterator() method on the entryset collection of the map.

    Type Parameters:
      `I` - the input type
      `O` - the output type
    Parameters:
      `map` - a map of predicates to transformers
    Returns:
      the `switch` transformer
    Throws:
      `NullPointerException` - if the map is null
      `NullPointerException` - if any transformer in the map is null
      `ClassCastException` - if the map elements are of the wrong type

  - ### switchTransformer

    public static <I, O> Transformer<I,O> switchTransformer(Predicate<? super I>[] predicates, Transformer<? super I,? extends O>[] transformers, Transformer<? super I,? extends O> defaultTransformer)
    Factory method that performs validation and copies the parameter arrays.
    Type Parameters:
      `I` - the input type
      `O` - the output type
    Parameters:
      `predicates` - array of predicates, cloned, no nulls
      `transformers` - matching array of transformers, cloned, no nulls
      `defaultTransformer` - the transformer to use if no match, null means return null
    Returns:
      the `chained` transformer
    Throws:
      `NullPointerException` - if either array is null
      `NullPointerException` - if any element in the arrays is null
      `IllegalArgumentException` - if the arrays have different sizes

  - ### getDefaultTransformer

    public Transformer<? super T,? extends R> getDefaultTransformer()
    Gets the default transformer.
    Returns:
      the default transformer
    Since:
      3.1

  - ### getPredicates

    public Predicate<? super T>[] getPredicates()
    Gets the predicates.
    Returns:
      a copy of the predicates
    Since:
      3.1

  - ### getTransformers

    public Transformer<? super T,? extends R>[] getTransformers()
    Gets the transformers.
    Returns:
      a copy of the transformers
    Since:
      3.1

  - ### transform

    public R transform(T input)
    Transforms the input to result by calling the transformer whose matching predicate returns true.
    Specified by:
      `transform` in interface `Transformer<T,R>`
    Parameters:
      `input` - the input object to transform
    Returns:
      the transformed result