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.BinaryProcedure;
022
023 /**
024 * Transposes (swaps) the arguments to some other
025 * {@link BinaryProcedure procedure}.
026 * For example, given a procedure <i>p</i>
027 * and the ordered pair of arguments <i>a</i>,
028 * <i>b</i>.
029 * {@link #run runs}
030 * <code>p.run(b,a)</code>.
031 * <p>
032 * Note that although this class implements
033 * {@link Serializable}, a given instance will
034 * only be truly <code>Serializable</code> if the
035 * underlying functor is. Attempts to serialize
036 * an instance whose delegate is not
037 * <code>Serializable</code> will result in an exception.
038 * </p>
039 * @version $Revision: 1156320 $ $Date: 2011-08-10 21:14:50 +0200 (Wed, 10 Aug 2011) $
040 * @author Rodney Waldhoff
041 */
042 public class TransposedProcedure<L, R> implements BinaryProcedure<L, R>, Serializable {
043 /**
044 * serialVersionUID declaration.
045 */
046 private static final long serialVersionUID = 4472683678460290015L;
047 // attributes
048 // ------------------------------------------------------------------------
049 private final BinaryProcedure<? super R, ? super L> procedure;
050
051 // constructor
052 // ------------------------------------------------------------------------
053 /**
054 * Create a new TransposedProcedure.
055 * @param procedure BinaryProcedure to transpose
056 */
057 public TransposedProcedure(BinaryProcedure<? super R, ? super L> procedure) {
058 if (procedure == null) {
059 throw new IllegalArgumentException("BinaryProcedure argument was null");
060 }
061 this.procedure = procedure;
062 }
063
064 // functor interface
065 // ------------------------------------------------------------------------
066 /**
067 * {@inheritDoc}
068 */
069 public void run(L left, R right) {
070 procedure.run(right, left);
071 }
072
073 /**
074 * {@inheritDoc}
075 */
076 public boolean equals(Object that) {
077 return that == this || (that instanceof TransposedProcedure<?, ?> && equals((TransposedProcedure<?, ?>) that));
078 }
079
080 /**
081 * Learn whether another TransposedProcedure is equal to this.
082 * @param that TransposedPredicate to test
083 * @return boolean
084 */
085 public boolean equals(TransposedProcedure<?, ?> that) {
086 return null != that && (null == procedure ? null == that.procedure : procedure.equals(that.procedure));
087 }
088
089 /**
090 * {@inheritDoc}
091 */
092 public int hashCode() {
093 int hash = "TransposedProcedure".hashCode();
094 if (null != procedure) {
095 hash ^= procedure.hashCode();
096 }
097 return hash;
098 }
099
100 /**
101 * {@inheritDoc}
102 */
103 public String toString() {
104 return "TransposedProcedure<" + procedure + ">";
105 }
106
107 // static
108 // ------------------------------------------------------------------------
109 /**
110 * Transpose a BinaryProcedure.
111 * @param p to transpose
112 * @return TransposedProcedure
113 */
114 public static <L, R> TransposedProcedure<R, L> transpose(BinaryProcedure<? super L, ? super R> p) {
115 return null == p ? null : new TransposedProcedure<R, L>(p);
116 }
117
118 }