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.core.composite;
18
19 import java.io.Serializable;
20
21 import org.apache.commons.functor.UnaryFunction;
22 import org.apache.commons.functor.UnaryPredicate;
23 import org.apache.commons.functor.adapter.UnaryPredicateUnaryFunction;
24 import org.apache.commons.lang3.Validate;
25
26 /**
27 * A {@link UnaryPredicate UnaryPredicate}
28 * representing the composition of
29 * {@link UnaryFunction UnaryFunctions},
30 * "chaining" the output of one to the input
31 * of another. For example,
32 * <pre>new CompositeUnaryPredicate(p).of(f)</pre>
33 * {@link #test tests} to
34 * <code>p.test(f.evaluate(obj))</code>, and
35 * <pre>new CompositeUnaryPredicate(p).of(f).of(g)</pre>
36 * {@link #test tests} to
37 * <code>p.test(f.evaluate(g.evaluate(obj)))</code>.
38 * <p>
39 * Note that although this class implements
40 * {@link Serializable}, a given instance will
41 * only be truly <code>Serializable</code> if all the
42 * underlying functors are. Attempts to serialize
43 * an instance whose delegates are not all
44 * <code>Serializable</code> will result in an exception.
45 * </p>
46 * @param <A> the predicate argument type.
47 * @version $Revision: 1345136 $ $Date: 2012-06-01 09:47:06 -0300 (Fri, 01 Jun 2012) $
48 */
49 public final class CompositeUnaryPredicate<A> implements UnaryPredicate<A>, Serializable {
50 /**
51 * serialVersionUID declaration.
52 */
53 private static final long serialVersionUID = 4880363949059265252L;
54 // attributes
55 // ------------------------------------------------------------------------
56 /**
57 * The adapted composite function.
58 */
59 private final CompositeUnaryFunction<? super A, Boolean> function;
60
61 // constructor
62 // ------------------------------------------------------------------------
63 /**
64 * Create a new CompositeUnaryPredicate.
65 * @param predicate UnaryPredicate against which the composite functions' output will be tested
66 */
67 public CompositeUnaryPredicate(UnaryPredicate<? super A> predicate) {
68 this.function =
69 new CompositeUnaryFunction<A, Boolean>(
70 new UnaryPredicateUnaryFunction<A>(Validate.notNull(predicate,
71 "predicate must not be null")));
72 }
73
74 /**
75 * Create a new CompositeUnaryPredicate.
76 * @param function delegate
77 */
78 private CompositeUnaryPredicate(CompositeUnaryFunction<? super A, Boolean> function) {
79 this.function = function;
80 }
81
82 // modifiers
83 // ------------------------------------------------------------------------
84 /**
85 * Fluently obtain a CompositeUnaryPredicate that applies our predicate to the result of the preceding function.
86 * @param <P> the input function left argument and output predicate argument types
87 * @param preceding UnaryFunction
88 * @return CompositeUnaryPredicate<P>
89 */
90 public <P> CompositeUnaryPredicate<P> of(UnaryFunction<? super P, ? extends A> preceding) {
91 return new CompositeUnaryPredicate<P>(function.of(preceding));
92 }
93
94 // predicate interface
95 // ------------------------------------------------------------------------
96 /**
97 * {@inheritDoc}
98 */
99 public boolean test(A obj) {
100 return function.evaluate(obj).booleanValue();
101 }
102
103 /**
104 * {@inheritDoc}
105 */
106 @Override
107 public boolean equals(Object that) {
108 return that == this || (that instanceof CompositeUnaryPredicate<?>
109 && equals((CompositeUnaryPredicate<?>) that));
110 }
111
112 /**
113 * Learn whether another CompositeUnaryPredicate is equal to this.
114 * @param that CompositeUnaryPredicate to test
115 * @return boolean
116 */
117 public boolean equals(CompositeUnaryPredicate<?> that) {
118 return null != that && function.equals(that.function);
119 }
120
121 /**
122 * {@inheritDoc}
123 */
124 @Override
125 public int hashCode() {
126 int hash = "CompositeUnaryPredicate".hashCode();
127 hash <<= 2;
128 hash ^= function.hashCode();
129 return hash;
130 }
131
132 /**
133 * {@inheritDoc}
134 */
135 @Override
136 public String toString() {
137 return "CompositeUnaryFunction<" + function + ">";
138 }
139
140 }