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 */
017package org.apache.commons.functor.core.composite;
018
019import java.io.Serializable;
020
021import org.apache.commons.functor.BinaryProcedure;
022import org.apache.commons.lang3.Validate;
023
024/**
025 * Transposes (swaps) the arguments to some other
026 * {@link BinaryProcedure procedure}.
027 * For example, given a procedure <i>p</i>
028 * and the ordered pair of arguments <i>a</i>,
029 * <i>b</i>.
030 * {@link #run runs}
031 * <code>p.run(b,a)</code>.
032 * <p>
033 * Note that although this class implements
034 * {@link Serializable}, a given instance will
035 * only be truly <code>Serializable</code> if the
036 * underlying functor is.  Attempts to serialize
037 * an instance whose delegate is not
038 * <code>Serializable</code> will result in an exception.
039 * </p>
040 * @param <L> the left argument type.
041 * @param <R> the right argument type.
042 * @version $Revision: 1365329 $ $Date: 2012-07-24 18:34:23 -0400 (Tue, 24 Jul 2012) $
043 */
044public class TransposedProcedure<L, R> implements BinaryProcedure<L, R>, Serializable {
045    /**
046     * serialVersionUID declaration.
047     */
048    private static final long serialVersionUID = 4472683678460290015L;
049    // attributes
050    // ------------------------------------------------------------------------
051    /**
052     * The adapted procedure.
053     */
054    private final BinaryProcedure<? super R, ? super L> procedure;
055
056    // constructor
057    // ------------------------------------------------------------------------
058    /**
059     * Create a new TransposedProcedure.
060     * @param procedure BinaryProcedure to transpose
061     */
062    public TransposedProcedure(BinaryProcedure<? super R, ? super L> procedure) {
063        this.procedure = Validate.notNull(procedure, "BinaryProcedure argument was null");
064    }
065
066    // functor interface
067    // ------------------------------------------------------------------------
068    /**
069     * {@inheritDoc}
070     */
071    public void run(L left, R right) {
072        procedure.run(right, left);
073    }
074
075    /**
076     * {@inheritDoc}
077     */
078    @Override
079    public boolean equals(Object that) {
080        return that == this || (that instanceof TransposedProcedure<?, ?> && equals((TransposedProcedure<?, ?>) that));
081    }
082
083    /**
084     * Learn whether another TransposedProcedure is equal to this.
085     * @param that TransposedPredicate to test
086     * @return boolean
087     */
088    public boolean equals(TransposedProcedure<?, ?> that) {
089        return null != that && procedure.equals(that.procedure);
090    }
091
092    /**
093     * {@inheritDoc}
094     */
095    @Override
096    public int hashCode() {
097        int hash = "TransposedProcedure".hashCode();
098        hash ^= procedure.hashCode();
099        return hash;
100    }
101
102    /**
103     * {@inheritDoc}
104     */
105    @Override
106    public String toString() {
107        return "TransposedProcedure<" + procedure + ">";
108    }
109
110    // static
111    // ------------------------------------------------------------------------
112    /**
113     * Transpose a BinaryProcedure.
114     *
115     * @param <L> the left argument type.
116     * @param <R> the right argument type.
117     * @param p to transpose
118     * @return TransposedProcedure
119     */
120    public static <L, R> TransposedProcedure<R, L> transpose(BinaryProcedure<? super L, ? super R> p) {
121        return null == p ? null : new TransposedProcedure<R, L>(p);
122    }
123
124}