1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.apache.commons.functor.adapter;
18
19 import java.io.Serializable;
20
21 import org.apache.commons.functor.BinaryFunction;
22 import org.apache.commons.functor.UnaryFunction;
23 import org.apache.commons.lang3.Validate;
24
25 /**
26 * Adapts a
27 * {@link BinaryFunction BinaryFunction}
28 * to the
29 * {@link UnaryFunction UnaryFunction} interface
30 * using a constant right-side argument.
31 * <p/>
32 * Note that although this class implements
33 * {@link Serializable}, a given instance will
34 * only be truly <code>Serializable</code> if the
35 * underlying objects are. Attempts to serialize
36 * an instance whose delegates are not
37 * <code>Serializable</code> will result in an exception.
38 *
39 * @param <A> the argument type.
40 * @param <T> the returned value type.
41 * @version $Revision: 1365377 $ $Date: 2012-07-24 21:59:23 -0300 (Tue, 24 Jul 2012) $
42 */
43 public final class RightBoundFunction<A, T> implements UnaryFunction<A, T>, Serializable {
44 /**
45 * serialVersionUID declaration.
46 */
47 private static final long serialVersionUID = -1313775632123661422L;
48 /** The {@link BinaryFunction BinaryFunction} I'm wrapping. */
49 private final BinaryFunction<? super A, Object, ? extends T> function;
50 /** The parameter to pass to {@code function}. */
51 private final Object param;
52
53 /**
54 * @param <R> bound arg type
55 * @param function the function to adapt
56 * @param arg the constant argument to use
57 */
58 @SuppressWarnings("unchecked")
59 public <R> RightBoundFunction(BinaryFunction<? super A, ? super R, ? extends T> function, R arg) {
60 this.function =
61 (BinaryFunction<? super A, Object, ? extends T>) Validate.notNull(
62 function, "left-hand BinaryFunction argument was null");
63 this.param = arg;
64 }
65
66 /**
67 * {@inheritDoc}
68 */
69 public T evaluate(A obj) {
70 return function.evaluate(obj, param);
71 }
72
73 /**
74 * {@inheritDoc}
75 */
76 @Override
77 public boolean equals(Object that) {
78 return that == this || (that instanceof RightBoundFunction<?, ?> && equals((RightBoundFunction<?, ?>) that));
79 }
80
81 /**
82 * Learn whether another RightBoundFunction is equal to this.
83 * @param that RightBoundFunction to test
84 * @return boolean
85 */
86 public boolean equals(RightBoundFunction<?, ?> that) {
87 return null != that
88 && function.equals(that.function)
89 && (null == param ? null == that.param : param.equals(that.param));
90 }
91
92 /**
93 * {@inheritDoc}
94 */
95 @Override
96 public int hashCode() {
97 int hash = "RightBoundFunction".hashCode();
98 hash <<= 2;
99 hash ^= function.hashCode();
100 if (null != param) {
101 hash <<= 2;
102 hash ^= param.hashCode();
103 }
104 return hash;
105 }
106
107 /**
108 * {@inheritDoc}
109 */
110 @Override
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 }