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.UnaryFunction;
023
024 /**
025 * Adapts a
026 * {@link BinaryFunction BinaryFunction}
027 * to the
028 * {@link UnaryFunction UnaryFunction} interface
029 * using a constant right-side 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 objects are. Attempts to serialize
035 * an instance whose delegates are not
036 * <code>Serializable</code> will result in an exception.
037 *
038 * @param <A> the argument type.
039 * @param <T> the returned value type.
040 * @version $Revision: 1157637 $ $Date: 2011-08-14 22:12:46 +0200 (Sun, 14 Aug 2011) $
041 * @author Rodney Waldhoff
042 */
043 public final class RightBoundFunction<A, T> implements UnaryFunction<A, T>, Serializable {
044 /**
045 * serialVersionUID declaration.
046 */
047 private static final long serialVersionUID = -1313775632123661422L;
048 /** The {@link BinaryFunction BinaryFunction} I'm wrapping. */
049 private final BinaryFunction<? super A, Object, ? extends T> function;
050 /** The parameter to pass to {@code function}. */
051 private final Object param;
052
053 /**
054 * @param <R> bound arg type
055 * @param function the function to adapt
056 * @param arg the constant argument to use
057 */
058 @SuppressWarnings("unchecked")
059 public <R> RightBoundFunction(BinaryFunction<? super A, ? super R, ? extends T> function, R arg) {
060 if (function == null) {
061 throw new IllegalArgumentException("left-hand BinaryFunction argument was null");
062 }
063 this.function = (BinaryFunction<? super A, Object, ? extends T>) function;
064 this.param = arg;
065 }
066
067 /**
068 * {@inheritDoc}
069 */
070 public T evaluate(A obj) {
071 return function.evaluate(obj, param);
072 }
073
074 /**
075 * {@inheritDoc}
076 */
077 public boolean equals(Object that) {
078 return that == this || (that instanceof RightBoundFunction<?, ?> && equals((RightBoundFunction<?, ?>) that));
079 }
080
081 /**
082 * Learn whether another RightBoundFunction is equal to this.
083 * @param that RightBoundFunction to test
084 * @return boolean
085 */
086 public boolean equals(RightBoundFunction<?, ?> that) {
087 return null != that
088 && (null == function ? null == that.function : function.equals(that.function))
089 && (null == param ? null == that.param : param.equals(that.param));
090 }
091
092 /**
093 * {@inheritDoc}
094 */
095 public int hashCode() {
096 int hash = "RightBoundFunction".hashCode();
097 if (null != function) {
098 hash <<= 2;
099 hash ^= function.hashCode();
100 }
101 if (null != param) {
102 hash <<= 2;
103 hash ^= param.hashCode();
104 }
105 return hash;
106 }
107
108 /**
109 * {@inheritDoc}
110 */
111 public String toString() {
112 return "RightBoundFunction<" + function + "(?," + param + ")>";
113 }
114
115 /**
116 * Adapt a BinaryFunction to the UnaryFunction interface.
117 * @param <L> the left argument type.
118 * @param <R> the right argument type.
119 * @param <T> the returned value type.
120 * @param function BinaryFunction to adapt
121 * @param arg Object that will always be used for the right side of the BinaryFunction delegate.
122 * @return RightBoundFunction
123 */
124 public static <L, R, T> RightBoundFunction<L, T> bind(BinaryFunction<? super L, ? super R, ? extends T> function,
125 R arg) {
126 return null == function ? null : new RightBoundFunction<L, T>(function, arg);
127 }
128
129 }