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.Function;
23 import org.apache.commons.lang3.Validate;
24
25 /**
26 * Adapts a
27 * {@link BinaryFunction BinaryFunction}
28 * to the
29 * {@link Function Function} interface
30 * using constant arguments.
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 <T> the returned value type.
40 * @version $Revision: 1365377 $ $Date: 2012-07-24 21:59:23 -0300 (Tue, 24 Jul 2012) $
41 */
42 public final class FullyBoundFunction<T> implements Function<T>, Serializable {
43 /**
44 * serialVersionUID declaration.
45 */
46 private static final long serialVersionUID = -8588331452137525985L;
47 /** The {@link BinaryFunction BinaryFunction} I'm wrapping. */
48 private final BinaryFunction<Object, Object, ? extends T> function;
49 /** The left parameter to pass to {@code function}. */
50 private final Object left;
51 /** The right parameter to pass to {@code function}. */
52 private final Object right;
53
54 /**
55 * Create a new FullyBoundFunction.
56 * @param <L> the left argument type.
57 * @param <R> the right argument type.
58 * @param function the function to adapt
59 * @param left the left side argument to use
60 * @param right the right side argument to use
61 */
62 @SuppressWarnings("unchecked")
63 public <L, R> FullyBoundFunction(BinaryFunction<? super L, ? super R, ? extends T> function, L left, R right) {
64 this.function =
65 (BinaryFunction<Object, Object, T>) Validate.notNull(function,
66 "BinaryFunction argument was null");
67 this.left = left;
68 this.right = right;
69 }
70
71 /**
72 * {@inheritDoc}
73 */
74 public T evaluate() {
75 return function.evaluate(left, right);
76 }
77
78 /**
79 * {@inheritDoc}
80 */
81 @Override
82 public boolean equals(Object that) {
83 return that == this || (that instanceof FullyBoundFunction<?> && equals((FullyBoundFunction<?>) that));
84 }
85
86 /**
87 * Learn whether another FullyBoundFunction is equal to this.
88 * @param that FullyBoundFunction to test
89 * @return boolean
90 */
91 public boolean equals(FullyBoundFunction<?> that) {
92 return null != that && function.equals(that.function)
93 && (null == left ? null == that.left : left.equals(that.left))
94 && (null == right ? null == that.right : right.equals(that.right));
95 }
96
97 /**
98 * {@inheritDoc}
99 */
100 @Override
101 public int hashCode() {
102 int hash = "FullyBoundFunction".hashCode();
103 hash <<= 2;
104 hash ^= function.hashCode();
105 hash <<= 2;
106 if (null != left) {
107 hash ^= left.hashCode();
108 }
109 hash <<= 2;
110 if (null != right) {
111 hash ^= right.hashCode();
112 }
113 return hash;
114 }
115
116 /**
117 * {@inheritDoc}
118 */
119 @Override
120 public String toString() {
121 return "FullyBoundFunction<" + function + "(" + left + ", " + right + ")>";
122 }
123
124 /**
125 * Adapt a BinaryFunction as a Function.
126 * @param <L> left type
127 * @param <R> right type
128 * @param <T> result type
129 * @param function to adapt
130 * @param left left side argument
131 * @param right right side argument
132 * @return FullyBoundFunction
133 */
134 public static <L, R, T> FullyBoundFunction<T> bind(
135 BinaryFunction<? super L, ? super R, ? extends T> function, L left, R right) {
136 return null == function ? null : new FullyBoundFunction<T>(function, left, right);
137 }
138
139 }