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
24 /**
25 * Adapts a
26 * {@link Function Function}
27 * to the
28 * {@link UnaryFunction UnaryFunction} interface
29 * by ignoring the unary argument.
30 * <p/>
31 * Note that although this class implements
32 * {@link Serializable}, a given instance will
33 * only be truly <code>Serializable</code> if the
34 * underlying functor is. Attempts to serialize
35 * an instance whose delegate is not
36 * <code>Serializable</code> will result in an exception.
37 *
38 * @param <A> the argument type.
39 * @param <T> the returned value type.
40 * @version $Revision: 1157609 $ $Date: 2011-08-14 21:42:21 +0200 (Sun, 14 Aug 2011) $
41 * @author Rodney Waldhoff
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 if (function == null) {
57 throw new IllegalArgumentException("Function argument was null");
58 }
59 this.function = function;
60 }
61
62 /**
63 * {@inheritDoc}
64 */
65 public T evaluate(A obj) {
66 return function.evaluate();
67 }
68
69 /**
70 * {@inheritDoc}
71 */
72 public boolean equals(Object that) {
73 return that == this || (that instanceof FunctionUnaryFunction<?, ?>
74 && equals((FunctionUnaryFunction<?, ?>) that));
75 }
76
77 /**
78 * Learn whether another FunctionUnaryFunction is equal to this.
79 * @param that FunctionUnaryFunction to test
80 * @return boolean
81 */
82 public boolean equals(FunctionUnaryFunction<?, ?> that) {
83 return null != that && (null == function ? null == that.function : function.equals(that.function));
84 }
85
86 /**
87 * {@inheritDoc}
88 */
89 public int hashCode() {
90 int hash = "FunctionUnaryFunction".hashCode();
91 if (null != function) {
92 hash ^= function.hashCode();
93 }
94 return hash;
95 }
96
97 /**
98 * {@inheritDoc}
99 */
100 public String toString() {
101 return "FunctionUnaryFunction<" + function + ">";
102 }
103
104 /**
105 * Adapt a Function to the UnaryFunction interface.
106 * @param <A> arg type
107 * @param <T> result type
108 * @param function to adapt
109 * @return FunctionUnaryFunction
110 */
111 public static <A, T> FunctionUnaryFunction<A, T> adapt(Function<? extends T> function) {
112 return null == function ? null : new FunctionUnaryFunction<A, T>(function);
113 }
114
115 }