/*

  * Licensed 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.functor.generator.util;

 import java.util.ArrayList;

 import java.util.Collection;

 import org.apache.commons.functor.UnaryFunction;

 import org.apache.commons.functor.UnaryProcedure;

 import org.apache.commons.functor.generator.Generator;

 /**

  * Transforms a generator into a collection. If a collection is not passed into

  * the constructor an ArrayList will be returned from the transform method.

  *

  * @param <E> the type of elements held in the adapted collection.

  * @since 1.0

  * @version $Revision: 1160793 $ $Date: 2011-08-23 18:48:32 +0200 (Tue, 23 Aug 2011) $

  * @author Jason Horman (jason@jhorman.org)

  */

 public class CollectionTransformer<E> implements UnaryFunction<Generator<? extends E>, Collection<? super E>> {

     /*

      * TODO revisit this class... it could stand a more-descriptive name.  Also, it's a little

      * hard to say whether, for an instance constructed without a specific target collection,

      * #evaluate() should return a new ArrayList for each call, or continue adding to

      * a single ArrayList instance (the current behavior).

      * Perhaps this is more a documentation issue than anything.

      */

     // instance methods

     //---------------------------------------------------

     /**

      * The adapted collection has to be filled.

      */

     private final Collection<? super E> toFill;

     // constructors

     //---------------------------------------------------

     /**

      * Create a new CollectionTransformer.

      */

     public CollectionTransformer() {

         this(null);

     }

     /**

      * Create a new CollectionTransformer.

      * @param toFill Collection to fill

      */

     public CollectionTransformer(Collection<? super E> toFill) {

         Collection<? super E> coll;

         if (toFill == null) {

             coll = new ArrayList<E>();

         } else {

             coll = toFill;

         }

         this.toFill = coll;

     }

     // instance methods

     //---------------------------------------------------

     /**

      * {@inheritDoc}

      */

     @SuppressWarnings("unchecked")

     public Collection<E> evaluate(Generator<? extends E> generator) {

         generator.run(new UnaryProcedure<E>() {

             public void run(E obj) {

                 toFill.add(obj);

             }

         });

         return (Collection<E>) toFill;

     }

 }