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;
18
19 /**
20 * Functor marker interface. All provided functor interfaces extend this interface.
21 * <p>
22 * Implementors are encouraged but not required to make their functors
23 * {@link java.io.Serializable Serializable}.
24 * </p>
25 *
26 * @since 1.0
27 * @version $Revision: 647297 $ $Date: 2008-04-11 22:14:50 +0200 (Fri, 11 Apr 2008) $
28 */
29 public interface Functor {
30
31 /**
32 * Returns a human readable description of this functor.
33 * Implementators are strongly encouraged but not
34 * strictly required to override the default {@link Object}
35 * implementation of this method.
36 *
37 * @return a human readable description of this functor
38 */
39 String toString();
40
41 /**
42 * Returns a hash code for this functor adhering to the
43 * general {@link Object#hashCode Object.hashCode} contract.
44 * Implementators are strongly encouraged but not
45 * strictly required to override the default {@link Object}
46 * implementation of this method.
47 *
48 * @see #equals
49 * @return a hash code for this functor
50 */
51 int hashCode();
52
53 /**
54 * Indicates whether some other object is "equal to"
55 * this functor. This method must adhere to
56 * general {@link Object#equals Object.equals} contract.
57 * Additionally, this method can return
58 * <tt>true</tt> <i>only</i> if the specified Object implements
59 * the same functor interface and is known to produce the same
60 * results and/or side-effects for the same arguments (if any).
61 * <p>
62 * While implementators are strongly encouraged to override
63 * the default Object implementation of this method,
64 * note that the default Object implementation
65 * does in fact adhere to the functor <code>equals</code> contract.
66 * </p>
67 * @param that the object to compare this functor to
68 * @see #hashCode
69 * @return <code>true</code> iff the given object implements
70 * this functor interface, and is known to produce the same
71 * results and/or side-effects for the same arguments
72 * (if any).
73 */
74 boolean equals(Object that);
75 }