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.adapter;
018    
019    import java.io.Serializable;
020    
021    import org.apache.commons.functor.BinaryPredicate;
022    import org.apache.commons.functor.UnaryPredicate;
023    
024    /**
025     * Adapts a
026     * {@link UnaryPredicate UnaryPredicate}
027     * to the
028     * {@link BinaryPredicate BinaryPredicate} interface
029     * by ignoring the first binary argument.
030     * <p/>
031     * Note that although this class implements
032     * {@link Serializable}, a given instance will
033     * only be truly <code>Serializable</code> if the
034     * underlying functor is.  Attempts to serialize
035     * an instance whose delegate is not
036     * <code>Serializable</code> will result in an exception.
037     *
038     * @param <L> the left argument type.
039     * @param <R> the right argument type.
040     * @version $Revision: 1157611 $ $Date: 2011-08-14 21:45:14 +0200 (Sun, 14 Aug 2011) $
041     * @author Rodney Waldhoff
042     */
043    public final class IgnoreLeftPredicate<L, R> implements BinaryPredicate<L, R>, Serializable {
044        /**
045         * serialVersionUID declaration.
046         */
047        private static final long serialVersionUID = -3200352647509255939L;
048        /** The {@link UnaryPredicate UnaryPredicate} I'm wrapping. */
049        private final UnaryPredicate<? super R> predicate;
050    
051        /**
052         * Create a new IgnoreLeftPredicate.
053         * @param predicate the right predicate
054         */
055        public IgnoreLeftPredicate(UnaryPredicate<? super R> predicate) {
056            if (predicate == null) {
057                throw new IllegalArgumentException("UnaryPredicate argument was null");
058            }
059            this.predicate = predicate;
060        }
061    
062        /**
063         * {@inheritDoc}
064         */
065        public boolean test(L left, R right) {
066            return predicate.test(right);
067        }
068    
069        /**
070         * {@inheritDoc}
071         */
072        public boolean equals(Object that) {
073            return that == this || (that instanceof IgnoreLeftPredicate<?, ?> && equals((IgnoreLeftPredicate<?, ?>) that));
074        }
075    
076        /**
077         * Learn whether another IgnoreLeftPredicate is equal to this.
078         * @param that the IgnoreLeftPredicate to test
079         * @return boolean
080         */
081        public boolean equals(IgnoreLeftPredicate<?, ?> that) {
082            return null != that && (null == predicate ? null == that.predicate : predicate.equals(that.predicate));
083        }
084    
085        /**
086         * {@inheritDoc}
087         */
088        public int hashCode() {
089            int hash = "IgnoreLeftPredicate".hashCode();
090            if (null != predicate) {
091                hash ^= predicate.hashCode();
092            }
093            return hash;
094        }
095    
096        /**
097         * {@inheritDoc}
098         */
099        public String toString() {
100            return "IgnoreLeftPredicate<" + predicate + ">";
101        }
102    
103        /**
104         * Adapt a UnaryPredicate to an IgnoreLeftPredicate.
105         * @param <L> left type
106         * @param <R> right type
107         * @param predicate to adapt
108         * @return IgnoreLeftPredicate<L, R>
109         */
110        public static <L, R> IgnoreLeftPredicate<L, R> adapt(UnaryPredicate<? super R> predicate) {
111            return null == predicate ? null : new IgnoreLeftPredicate<L, R>(predicate);
112        }
113    
114    }