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.collections4.functors;
18
19 import java.io.Serializable;
20 import java.util.Objects;
21
22 import org.apache.commons.collections4.Equator;
23
24 /**
25 * Default {@link Equator} implementation.
26 *
27 * @param <T> the types of object this {@link Equator} can evaluate.
28 * @since 4.0
29 */
30 public class DefaultEquator<T> implements Equator<T>, Serializable {
31
32 /** Serial version UID */
33 private static final long serialVersionUID = 825802648423525485L;
34
35 /** Static instance */
36 @SuppressWarnings("rawtypes") // the static instance works for all types
37 public static final DefaultEquator INSTANCE = new DefaultEquator<>();
38
39 /**
40 * Hashcode used for {@code null} objects.
41 */
42 public static final int HASHCODE_NULL = -1;
43
44 /**
45 * Factory returning the typed singleton instance.
46 *
47 * @param <T> the object type
48 * @return the singleton instance
49 */
50 public static <T> DefaultEquator<T> defaultEquator() {
51 return DefaultEquator.INSTANCE;
52 }
53
54 /**
55 * Restricted constructor.
56 */
57 private DefaultEquator() {
58 }
59
60 /**
61 * {@inheritDoc} Delegates to {@link Objects#equals(Object, Object)}.
62 */
63 @Override
64 public boolean equate(final T o1, final T o2) {
65 return Objects.equals(o1, o2);
66 }
67
68 /**
69 * {@inheritDoc}
70 *
71 * @return {@code o.hashCode()} if {@code o} is non-
72 * {@code null}, else {@link #HASHCODE_NULL}.
73 */
74 @Override
75 public int hash(final T o) {
76 return o == null ? HASHCODE_NULL : o.hashCode();
77 }
78
79 private Object readResolve() {
80 return INSTANCE;
81 }
82
83 }