org.apache.commons.collections

## Class FactoryUtils

- java.lang.Object
- - org.apache.commons.collections.FactoryUtils

-     public class FactoryUtils
      extends Object

  `FactoryUtils` provides reference implementations and utilities for the Factory functor interface. The supplied factories are:
  - Prototype - clones a specified object
  - Reflection - creates objects using reflection
  - Constant - always returns the same object
  - Null - always returns null
  - Exception - always throws an exception
  All the supplied factories are Serializable.
  Since:
    Commons Collections 3.0
  Version:
    $Revision: 646777 $ $Date: 2008-04-10 14:33:15 +0200 (Thu, 10 Apr 2008) $
  Author:
    Stephen Colebourne

- - ### Constructor Summary

    Constructors
    Constructor and Description
    `FactoryUtils()` This class is not normally instantiated.

  - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `static Factory` | `constantFactory(Object constantToReturn)` Creates a Factory that will return the same object each time the factory is used.
    `static Factory` | `exceptionFactory()` Gets a Factory that always throws an exception.
    `static Factory` | `instantiateFactory(Class classToInstantiate)` Creates a Factory that can create objects of a specific type using a no-args constructor.
    `static Factory` | `instantiateFactory(Class classToInstantiate, Class[] paramTypes, Object[] args)` Creates a Factory that can create objects of a specific type using the arguments specified to this method.
    `static Factory` | `nullFactory()` Gets a Factory that will return null each time the factory is used.
    `static Factory` | `prototypeFactory(Object prototype)` Creates a Factory that will return a clone of the same prototype object each time the factory is used.

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

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

- - ### Constructor Detail

    - #### FactoryUtils

          public FactoryUtils()

      This class is not normally instantiated.

  - ### Method Detail

    - #### exceptionFactory

          public static Factory exceptionFactory()

      Gets a Factory that always throws an exception. This could be useful during testing as a placeholder.
      Returns:
        the factory
      See Also:
        `ExceptionFactory`

    - #### nullFactory

          public static Factory nullFactory()

      Gets a Factory that will return null each time the factory is used. This could be useful during testing as a placeholder.
      Returns:
        the factory
      See Also:
        `ConstantFactory`

    - #### constantFactory

          public static Factory constantFactory(Object constantToReturn)

      Creates a Factory that will return the same object each time the factory is used. 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.
      Parameters:
        `constantToReturn` - the constant object to return each time in the factory
      Returns:
        the `constant` factory.
      See Also:
        `ConstantFactory`

    - #### prototypeFactory

          public static Factory prototypeFactory(Object prototype)

      Creates a Factory that will return a clone of the same prototype object each time the factory is used. The prototype will be cloned using one of these techniques (in order):
      - public clone method
      - public copy constructor
      - serialization clone
      Parameters:
        `prototype` - the object to clone each time in the factory
      Returns:
        the `prototype` factory
      Throws:
        `IllegalArgumentException` - if the prototype is null
        `IllegalArgumentException` - if the prototype cannot be cloned
      See Also:
        `PrototypeFactory`

    - #### instantiateFactory

          public static Factory instantiateFactory(Class classToInstantiate)

      Creates a Factory that can create objects of a specific type using a no-args constructor.
      Parameters:
        `classToInstantiate` - the Class to instantiate each time in the factory
      Returns:
        the `reflection` factory
      Throws:
        `IllegalArgumentException` - if the classToInstantiate is null
      See Also:
        `InstantiateFactory`

    - #### instantiateFactory

          public static Factory instantiateFactory(Class classToInstantiate,
                                   Class[] paramTypes,
                                   Object[] args)

      Creates a Factory that can create objects of a specific type using the arguments specified to this method.
      Parameters:
        `classToInstantiate` - the Class to instantiate each time in the factory
        `paramTypes` - parameter types for the constructor, can be null
        `args` - the arguments to pass to the constructor, can be null
      Returns:
        the `reflection` factory
      Throws:
        `IllegalArgumentException` - if the classToInstantiate is null
        `IllegalArgumentException` - if the paramTypes and args don't match
        `IllegalArgumentException` - if the constructor doesn't exist
      See Also:
        `InstantiateFactory`

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