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.Function;
22 import org.apache.commons.functor.Predicate;
23
24 /**
25 * Adapts a <code>Boolean</code>-valued
26 * {@link Function Function} to the
27 * {@link Predicate Predicate} interface.
28 * <p/>
29 * Note that although this class implements
30 * {@link Serializable}, a given instance will
31 * only be truly <code>Serializable</code> if the
32 * underlying functor is. Attempts to serialize
33 * an instance whose delegate is not
34 * <code>Serializable</code> will result in an exception.
35 *
36 * @version $Revision: 1157608 $ $Date: 2011-08-14 21:40:57 +0200 (Sun, 14 Aug 2011) $
37 * @author Rodney Waldhoff
38 */
39 public final class FunctionPredicate implements Predicate, Serializable {
40
41 /**
42 * serialVersionUID declaration.
43 */
44 private static final long serialVersionUID = 6564796937660102222L;
45 /** The {@link Function Function} I'm wrapping. */
46 private final Function<Boolean> function;
47
48 /**
49 * Create a new FunctionPredicate.
50 * @param function to adapt
51 */
52 public FunctionPredicate(Function<Boolean> function) {
53 if (function == null) {
54 throw new IllegalArgumentException("Function argument was null");
55 }
56 this.function = function;
57 }
58
59 /**
60 * Returns the <code>boolean</code> value of the non-<code>null</code>
61 * <code>Boolean</code> returned by the {@link Function#evaluate evaluate}
62 * method of my underlying function.
63 * {@inheritDoc}
64 */
65 public boolean test() {
66 return function.evaluate();
67 }
68
69 /**
70 * {@inheritDoc}
71 */
72 public boolean equals(Object that) {
73 return that == this || (that instanceof FunctionPredicate && equals((FunctionPredicate) that));
74 }
75
76 /**
77 * Learn whether another FunctionPredicate is equal to this.
78 * @param that FunctionPredicate to test
79 * @return boolean
80 */
81 public boolean equals(FunctionPredicate that) {
82 return null != that && (null == function ? null == that.function : function.equals(that.function));
83 }
84
85 /**
86 * {@inheritDoc}
87 */
88 public int hashCode() {
89 int hash = "FunctionPredicate".hashCode();
90 if (null != function) {
91 hash ^= function.hashCode();
92 }
93 return hash;
94 }
95
96 /**
97 * {@inheritDoc}
98 */
99 public String toString() {
100 return "FunctionPredicate<" + function + ">";
101 }
102
103 /**
104 * Adapt a Function as a Predicate.
105 * @param function to adapt
106 * @return FunctionPredicate
107 */
108 public static FunctionPredicate adapt(Function<Boolean> function) {
109 return null == function ? null : new FunctionPredicate(function);
110 }
111 }