001    /*
002     * Licensed to the Apache Software Foundation (ASF) under one or more
003     * contributor license agreements.  See the NOTICE file distributed with
004     * this work for additional information regarding copyright ownership.
005     * The ASF licenses this file to You under the Apache License, Version 2.0
006     * (the "License"); you may not use this file except in compliance with
007     * the License.  You may obtain a copy of the License at
008     *
009     *      http://www.apache.org/licenses/LICENSE-2.0
010     *
011     * Unless required by applicable law or agreed to in writing, software
012     * distributed under the License is distributed on an "AS IS" BASIS,
013     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014     * See the License for the specific language governing permissions and
015     * limitations under the License.
016     */
017    package org.apache.commons.functor.core.composite;
018    
019    import java.io.Serializable;
020    
021    import org.apache.commons.functor.Function;
022    import org.apache.commons.functor.UnaryFunction;
023    
024    /**
025     * A Function whose result is then run through a UnaryFunction.
026     * @version $Revision: 1171154 $ $Date: 2011-09-15 17:58:38 +0200 (Thu, 15 Sep 2011) $
027     * @author Matt Benson
028     */
029    public class TransformedFunction<T> implements Function<T>, Serializable {
030        /**
031         * serialVersionUID declaration.
032         */
033        private static final long serialVersionUID = 1201423110871342081L;
034    
035        /**
036         * Type-remembering helper
037         * @param <X>
038         */
039        private static final class Helper<X, T> implements Function<T>, Serializable {
040            /**
041             * serialVersionUID declaration.
042             */
043            private static final long serialVersionUID = -7177784125292465809L;
044            private Function<? extends X> preceding;
045            private UnaryFunction<? super X, ? extends T> following;
046    
047            /**
048             * Create a new Helper.
049             * @param preceding Function
050             * @param following UnaryFunction
051             */
052            private Helper(Function<? extends X> preceding, UnaryFunction<? super X, ? extends T> following) {
053                this.preceding = preceding;
054                this.following = following;
055            }
056    
057            /**
058             * {@inheritDoc}
059             */
060            public T evaluate() {
061                return following.evaluate(preceding.evaluate());
062            }
063        }
064    
065        private final Helper<?, T> helper;
066    
067        /**
068         * Create a new TransformedFunction.
069         * @param <X>
070         * @param preceding Function
071         * @param following UnaryFunction
072         */
073        public <X> TransformedFunction(Function<? extends X> preceding,
074                UnaryFunction<? super X, ? extends T> following) {
075            this.helper = new Helper<X, T>(preceding, following);
076        }
077    
078        /**
079         * {@inheritDoc}
080         */
081        public final T evaluate() {
082            return helper.evaluate();
083        }
084    
085        /**
086         * {@inheritDoc}
087         */
088        @Override
089        public final boolean equals(Object obj) {
090            return obj == this || obj instanceof TransformedFunction<?> && equals((TransformedFunction<?>) obj);
091        }
092    
093        /**
094         * Learn whether another TransformedFunction is equal to <code>this</code>.
095         * @param that instance to test
096         * @return whether equal
097         */
098        public final boolean equals(TransformedFunction<?> that) {
099            return that != null && that.helper.preceding.equals(this.helper.preceding)
100                    && that.helper.following.equals(this.helper.following);
101        }
102    
103        /**
104         * {@inheritDoc}
105         */
106        @Override
107        public int hashCode() {
108            int result = "TransformedFunction".hashCode();
109            result <<= 2;
110            result |= helper.following.hashCode();
111            result <<= 2;
112            result |= helper.preceding.hashCode();
113            return result;
114        }
115    
116        /**
117         * {@inheritDoc}
118         */
119        @Override
120        public String toString() {
121            return "TransformedFunction<" + helper.preceding + "; " + helper.following + ">";
122        }
123    }