org.apache.commons.collections.functors

## Class ConstantTransformer

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

- All Implemented Interfaces:
    Serializable, Transformer

      public class ConstantTransformer
      extends Object
      implements Transformer, Serializable

  Transformer implementation that returns the same constant each time.

  No check is made that the object is immutable. In general, only immutable objects should use the constant factory. Mutable objects should use the prototype factory.

  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

- - ### Field Summary

    Fields
    Modifier and Type | Field and Description
    --- | ---
    `static Transformer` | `NULL_INSTANCE` Returns null each time

  - ### Constructor Summary

    Constructors
    Constructor and Description
    `ConstantTransformer(Object constantToReturn)` Constructor that performs no validation.

  - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `Object` | `getConstant()` Gets the constant.
    `static Transformer` | `getInstance(Object constantToReturn)` Transformer method that performs validation.
    `Object` | `transform(Object input)` Transforms the input by ignoring it and returning the stored constant instead.

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

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

- - ### Field Detail

    - #### NULL_INSTANCE

          public static final Transformer NULL_INSTANCE

      Returns null each time

  - ### Constructor Detail

    - #### ConstantTransformer

          public ConstantTransformer(Object constantToReturn)

      Constructor that performs no validation. Use `getInstance` if you want that.
      Parameters:
        `constantToReturn` - the constant to return each time

  - ### Method Detail

    - #### getInstance

          public static Transformer getInstance(Object constantToReturn)

      Transformer method that performs validation.
      Parameters:
        `constantToReturn` - the constant object to return each time in the factory
      Returns:
        the `constant` factory.

    - #### transform

          public Object transform(Object input)

      Transforms the input by ignoring it and returning the stored constant instead.
      Specified by:
        `transform` in interface `Transformer`
      Parameters:
        `input` - the input object which is ignored
      Returns:
        the stored constant

    - #### getConstant

          public Object getConstant()

      Gets the constant.
      Returns:
        the constant
      Since:
        Commons Collections 3.1

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