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.UnaryFunction;
23 import org.apache.commons.lang3.Validate;
24
25 /**
26 * Adapts a
27 * {@link Function Function}
28 * to the
29 * {@link UnaryFunction UnaryFunction} interface
30 * by ignoring the unary 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 functor is. Attempts to serialize
36 * an instance whose delegate is 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 FunctionUnaryFunction<A, T> implements UnaryFunction<A, T>, Serializable {
44 /**
45 * serialVersionUID declaration.
46 */
47 private static final long serialVersionUID = 1993899041200996524L;
48 /** The {@link Function Function} I'm wrapping. */
49 private final Function<? extends T> function;
50
51 /**
52 * Create a new FunctionUnaryFunction.
53 * @param function to adapt
54 */
55 public FunctionUnaryFunction(Function<? extends T> function) {
56 this.function = Validate.notNull(function, "Function argument was null");
57 }
58
59 /**
60 * {@inheritDoc}
61 */
62 public T evaluate(A obj) {
63 return function.evaluate();
64 }
65
66 /**
67 * {@inheritDoc}
68 */
69 @Override
70 public boolean equals(Object that) {
71 return that == this || (that instanceof FunctionUnaryFunction<?, ?>
72 && equals((FunctionUnaryFunction<?, ?>) that));
73 }
74
75 /**
76 * Learn whether another FunctionUnaryFunction is equal to this.
77 * @param that FunctionUnaryFunction to test
78 * @return boolean
79 */
80 public boolean equals(FunctionUnaryFunction<?, ?> that) {
81 return null != that && function.equals(that.function);
82 }
83
84 /**
85 * {@inheritDoc}
86 */
87 @Override
88 public int hashCode() {
89 int hash = "FunctionUnaryFunction".hashCode();
90 hash ^= function.hashCode();
91 return hash;
92 }
93
94 /**
95 * {@inheritDoc}
96 */
97 @Override
98 public String toString() {
99 return "FunctionUnaryFunction<" + function + ">";
100 }
101
102 /**
103 * Adapt a Function to the UnaryFunction interface.
104 * @param <A> arg type
105 * @param <T> result type
106 * @param function to adapt
107 * @return FunctionUnaryFunction
108 */
109 public static <A, T> FunctionUnaryFunction<A, T> adapt(Function<? extends T> function) {
110 return null == function ? null : new FunctionUnaryFunction<A, T>(function);
111 }
112
113 }