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.BinaryFunction;
022 import org.apache.commons.functor.BinaryProcedure;
023
024 /**
025 * Adapts a
026 * {@link BinaryProcedure BinaryProcedure}
027 * to the
028 * {@link BinaryFunction BinaryFunction} interface
029 * by always returning <code>null</code>.
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 procedure 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 * @param <T> the returned value type.
041 * @version $Revision: 1157600 $ $Date: 2011-08-14 21:22:50 +0200 (Sun, 14 Aug 2011) $
042 * @author Rodney Waldhoff
043 */
044 public final class BinaryProcedureBinaryFunction<L, R, T> implements BinaryFunction<L, R, T>, Serializable {
045 /**
046 * serialVersionUID declaration.
047 */
048 private static final long serialVersionUID = 2099210273403668624L;
049 /** The {@link BinaryProcedure BinaryProcedure} I'm wrapping. */
050 private final BinaryProcedure<? super L, ? super R> procedure;
051
052 /**
053 * Create a new BinaryProcedureBinaryFunction.
054 * @param procedure to adapt as a BinaryFunction
055 */
056 public BinaryProcedureBinaryFunction(BinaryProcedure<? super L, ? super R> procedure) {
057 if (procedure == null) {
058 throw new IllegalArgumentException("BinaryProcedure argument was null");
059 }
060 this.procedure = procedure;
061 }
062
063 /**
064 * {@inheritDoc}
065 */
066 public T evaluate(L left, R right) {
067 procedure.run(left, right);
068 return null;
069 }
070
071 /**
072 * {@inheritDoc}
073 */
074 public boolean equals(Object that) {
075 return that == this || (that instanceof BinaryProcedureBinaryFunction<?, ?, ?>
076 && equals((BinaryProcedureBinaryFunction<?, ?, ?>) that));
077 }
078
079 /**
080 * Learn whether another BinaryProcedureBinaryFunction is equal to this.
081 * @param that the BinaryProcedureBinaryFunction to test
082 * @return boolean
083 */
084 public boolean equals(BinaryProcedureBinaryFunction<?, ?, ?> that) {
085 return null != that && (null == procedure ? null == that.procedure : procedure.equals(that.procedure));
086 }
087
088 /**
089 * {@inheritDoc}
090 */
091 public int hashCode() {
092 int hash = "BinaryProcedureBinaryFunction".hashCode();
093 if (null != procedure) {
094 hash ^= procedure.hashCode();
095 }
096 return hash;
097 }
098
099 /**
100 * {@inheritDoc}
101 */
102 public String toString() {
103 return "BinaryProcedureBinaryFunction<" + procedure + ">";
104 }
105
106 /**
107 * Adapt the given, possibly-<code>null</code>,
108 * {@link BinaryProcedure BinaryProcedure} to the
109 * {@link BinaryFunction BinaryFunction} interface.
110 * When the given <code>BinaryProcedure</code> is <code>null</code>,
111 * returns <code>null</code>.
112 *
113 * @param <L> the left argument type.
114 * @param <R> the right argument type.
115 * @param <T> the returned value type.
116 * @param procedure the possibly-<code>null</code>
117 * {@link BinaryFunction BinaryFunction} to adapt
118 * @return a <code>BinaryProcedureBinaryFunction</code> wrapping the given
119 * {@link BinaryFunction BinaryFunction}, or <code>null</code>
120 * if the given <code>BinaryFunction</code> is <code>null</code>
121 */
122 public static <L, R, T> BinaryProcedureBinaryFunction<L, R, T> adapt(BinaryProcedure<? super L, ? super R> procedure) {
123 return null == procedure ? null : new BinaryProcedureBinaryFunction<L, R, T>(procedure);
124 }
125
126 }