org.apache.commons.collections.functors

## Class SwitchTransformer

- java.lang.Object
- - org.apache.commons.collections.functors.SwitchTransformer

- All Implemented Interfaces:
    Serializable, Transformer

      public class SwitchTransformer
      extends Object
      implements Transformer, Serializable

  Transformer implementation calls the transformer whose predicate returns true, like a switch statement.
  Since:
    Commons Collections 3.0
  Version:
    $Revision: 646777 $ $Date: 2008-04-10 14:33:15 +0200 (Thu, 10 Apr 2008) $
  Author:
    Stephen Colebourne
  See Also:
    Serialized Form

- - ### Constructor Summary

    Constructors
    Constructor and Description
    `SwitchTransformer(Predicate[] predicates, Transformer[] transformers, Transformer defaultTransformer)` Constructor that performs no validation.

  - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `Transformer` | `getDefaultTransformer()` Gets the default transformer.
    `static Transformer` | `getInstance(Map predicatesAndTransformers)` Create a new Transformer that calls one of the transformers depending on the predicates.
    `static Transformer` | `getInstance(Predicate[] predicates, Transformer[] transformers, Transformer defaultTransformer)` Factory method that performs validation and copies the parameter arrays.
    `Predicate[]` | `getPredicates()` Gets the predicates, do not modify the array.
    `Transformer[]` | `getTransformers()` Gets the transformers, do not modify the array.
    `Object` | `transform(Object 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`

- - ### Constructor Detail

    - #### SwitchTransformer

          public SwitchTransformer(Predicate[] predicates,
                           Transformer[] transformers,
                           Transformer defaultTransformer)

      Constructor that performs no validation. Use `getInstance` if you want that.
      Parameters:
        `predicates` - array of predicates, not cloned, no nulls
        `transformers` - matching array of transformers, not cloned, no nulls
        `defaultTransformer` - the transformer to use if no match, null means return null

  - ### Method Detail

    - #### getInstance

          public static Transformer getInstance(Predicate[] predicates,
                                Transformer[] transformers,
                                Transformer defaultTransformer)

      Factory method that performs validation and copies the parameter arrays.
      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:
        `IllegalArgumentException` - if array is null
        `IllegalArgumentException` - if any element in the array is null

    - #### getInstance

          public static Transformer getInstance(Map predicatesAndTransformers)

      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.

      Parameters:
        `predicatesAndTransformers` - a map of predicates to transformers
      Returns:
        the `switch` transformer
      Throws:
        `IllegalArgumentException` - if the map is null
        `IllegalArgumentException` - if any transformer in the map is null
        `ClassCastException` - if the map elements are of the wrong type

    - #### transform

          public Object transform(Object input)

      Transforms the input to result by calling the transformer whose matching predicate returns true.
      Specified by:
        `transform` in interface `Transformer`
      Parameters:
        `input` - the input object to transform
      Returns:
        the transformed result

    - #### getPredicates

          public Predicate[] getPredicates()

      Gets the predicates, do not modify the array.
      Returns:
        the predicates
      Since:
        Commons Collections 3.1

    - #### getTransformers

          public Transformer[] getTransformers()

      Gets the transformers, do not modify the array.
      Returns:
        the transformers
      Since:
        Commons Collections 3.1

    - #### getDefaultTransformer

          public Transformer getDefaultTransformer()

      Gets the default transformer.
      Returns:
        the default transformer
      Since:
        Commons Collections 3.1

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