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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.commons.collections4;

import org.apache.commons.collections4.functors.ConstantFactory;
import org.apache.commons.collections4.functors.ExceptionFactory;
import org.apache.commons.collections4.functors.InstantiateFactory;
import org.apache.commons.collections4.functors.PrototypeFactory;

/**
 * FactoryUtils provides reference implementations and utilities
 * for the Factory functor interface. The supplied factories are:
 * 
    *
  • Prototype - clones a specified object *
  • Instantiate - creates objects using reflection *
  • Constant - always returns the same object *
  • Null - always returns null *
  • Exception - always throws an exception *
*

* Since v4.1 only factories which are considered to be unsafe are * Serializable. Factories considered to be unsafe for serialization are: *

    *
  • Prototype *
  • Instantiate *
* * @since 3.0 * @version $Id: FactoryUtils.java 1714362 2015-11-14 20:38:02Z tn $ */ public class FactoryUtils { /** * This class is not normally instantiated. */ private FactoryUtils() {} /** * Gets a Factory that always throws an exception. * This could be useful during testing as a placeholder. * * @see org.apache.commons.collections4.functors.ExceptionFactory * * @param the type that the factory creates * @return the factory */ public static Factory exceptionFactory() { return ExceptionFactory.exceptionFactory(); } /** * Gets a Factory that will return null each time the factory is used. * This could be useful during testing as a placeholder. * * @see org.apache.commons.collections4.functors.ConstantFactory * @param the "type" of null object the factory should return. * @return the factory */ public static Factory nullFactory() { return ConstantFactory.constantFactory(null); } /** * 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. * * @see org.apache.commons.collections4.functors.ConstantFactory * * @param the type that the factory creates * @param constantToReturn the constant object to return each time in the factory * @return the constant factory. */ public static Factory constantFactory(final T constantToReturn) { return ConstantFactory.constantFactory(constantToReturn); } /** * 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 *
      * * @see org.apache.commons.collections4.functors.PrototypeFactory * * @param the type that the factory creates * @param prototype the object to clone each time in the factory * @return the prototype factory, or a {@link ConstantFactory#NULL_INSTANCE} if * the {@code prototype} is {@code null} * @throws IllegalArgumentException if the prototype cannot be cloned */ public static Factory prototypeFactory(final T prototype) { return PrototypeFactory.prototypeFactory(prototype); } /** * Creates a Factory that can create objects of a specific type using * a no-args constructor. * * @see org.apache.commons.collections4.functors.InstantiateFactory * * @param the type that the factory creates * @param classToInstantiate the Class to instantiate each time in the factory * @return the reflection factory * @throws NullPointerException if the classToInstantiate is null */ public static Factory instantiateFactory(final Class classToInstantiate) { return InstantiateFactory.instantiateFactory(classToInstantiate, null, null); } /** * Creates a Factory that can create objects of a specific type using * the arguments specified to this method. * * @see org.apache.commons.collections4.functors.InstantiateFactory * * @param the type that the factory creates * @param classToInstantiate the Class to instantiate each time in the factory * @param paramTypes parameter types for the constructor, can be null * @param args the arguments to pass to the constructor, can be null * @return the reflection factory * @throws NullPointerException if the classToInstantiate is null * @throws IllegalArgumentException if the paramTypes and args don't match * @throws IllegalArgumentException if the constructor doesn't exist */ public static Factory instantiateFactory(final Class classToInstantiate, final Class[] paramTypes, final Object[] args) { return InstantiateFactory.instantiateFactory(classToInstantiate, paramTypes, args); } }




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