001 /*
002 * Licensed under the Apache License, Version 2.0 (the "License");
003 * you may not use this file except in compliance with the License.
004 * You may obtain a copy of the License at
005 *
006 * http://www.apache.org/licenses/LICENSE-2.0
007 *
008 * Unless required by applicable law or agreed to in writing, software
009 * distributed under the License is distributed on an "AS IS" BASIS,
010 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
011 * See the License for the specific language governing permissions and
012 * limitations under the License.
013 */
014
015 package org.apache.commons.functor.generator.util;
016
017 import java.util.ArrayList;
018 import java.util.Collection;
019
020 import org.apache.commons.functor.UnaryFunction;
021 import org.apache.commons.functor.UnaryProcedure;
022 import org.apache.commons.functor.generator.Generator;
023
024 /**
025 * Transforms a generator into a collection. If a collection is not passed into
026 * the constructor an ArrayList will be returned from the transform method.
027 *
028 * @param <E> the type of elements held in the adapted collection.
029 * @since 1.0
030 * @version $Revision: 1160793 $ $Date: 2011-08-23 18:48:32 +0200 (Tue, 23 Aug 2011) $
031 * @author Jason Horman (jason@jhorman.org)
032 */
033 public class CollectionTransformer<E> implements UnaryFunction<Generator<? extends E>, Collection<? super E>> {
034 /*
035 * TODO revisit this class... it could stand a more-descriptive name. Also, it's a little
036 * hard to say whether, for an instance constructed without a specific target collection,
037 * #evaluate() should return a new ArrayList for each call, or continue adding to
038 * a single ArrayList instance (the current behavior).
039 * Perhaps this is more a documentation issue than anything.
040 */
041
042 // instance methods
043 //---------------------------------------------------
044 /**
045 * The adapted collection has to be filled.
046 */
047 private final Collection<? super E> toFill;
048
049 // constructors
050 //---------------------------------------------------
051 /**
052 * Create a new CollectionTransformer.
053 */
054 public CollectionTransformer() {
055 this(null);
056 }
057
058 /**
059 * Create a new CollectionTransformer.
060 * @param toFill Collection to fill
061 */
062 public CollectionTransformer(Collection<? super E> toFill) {
063 Collection<? super E> coll;
064 if (toFill == null) {
065 coll = new ArrayList<E>();
066 } else {
067 coll = toFill;
068 }
069 this.toFill = coll;
070 }
071
072 // instance methods
073 //---------------------------------------------------
074 /**
075 * {@inheritDoc}
076 */
077 @SuppressWarnings("unchecked")
078 public Collection<E> evaluate(Generator<? extends E> generator) {
079 generator.run(new UnaryProcedure<E>() {
080 public void run(E obj) {
081 toFill.add(obj);
082 }
083 });
084 return (Collection<E>) toFill;
085 }
086 }