## org.apache.commons.collections
Class FactoryUtils

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

    public class FactoryUtils

extends java.lang.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 13:33:15 +0100 (Thu, 10 Apr 2008) $
Author:
  Stephen Colebourne

Constructor Summary
`FactoryUtils()` This class is not normally instantiated.

Method Summary
`static Factory` `constantFactory(java.lang.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(java.lang.Class classToInstantiate)` Creates a Factory that can create objects of a specific type using a no-args constructor.
`static Factory` `instantiateFactory(java.lang.Class classToInstantiate, java.lang.Class[] paramTypes, java.lang.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(java.lang.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(java.lang.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(java.lang.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:
    `java.lang.IllegalArgumentException` - if the prototype is null
    `java.lang.IllegalArgumentException` - if the prototype cannot be cloned
  See Also:
    `PrototypeFactory`

### instantiateFactory

    public static Factory instantiateFactory(java.lang.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:
    `java.lang.IllegalArgumentException` - if the classToInstantiate is null
  See Also:
    `InstantiateFactory`

### instantiateFactory

    public static Factory instantiateFactory(java.lang.Class classToInstantiate,
                                             java.lang.Class[] paramTypes,
                                             java.lang.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:
    `java.lang.IllegalArgumentException` - if the classToInstantiate is null
    `java.lang.IllegalArgumentException` - if the paramTypes and args don't match
    `java.lang.IllegalArgumentException` - if the constructor doesn't exist
  See Also:
    `InstantiateFactory`

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