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.lang3.builder;
18
19 /**
20 * {@link Diffable} classes can be compared with other objects
21 * for differences. The {@link DiffResult} object retrieved can be queried
22 * for a list of differences or printed using the {@link DiffResult#toString()}.
23 *
24 * <p>The calculation of the differences is <i>consistent with equals</i> if
25 * and only if {@code d1.equals(d2)} implies {@code d1.diff(d2) == ""}.
26 * It is strongly recommended that implementations are consistent with equals
27 * to avoid confusion. Note that {@code null} is not an instance of any class
28 * and {@code d1.diff(null)} should throw a {@link NullPointerException}.</p>
29 *
30 * <p>
31 * {@link Diffable} classes lend themselves well to unit testing, in which a
32 * easily readable description of the differences between an anticipated result and
33 * an actual result can be retrieved. For example:
34 * </p>
35 * <pre>
36 * Assert.assertEquals(expected.diff(result), expected, result);
37 * </pre>
38 *
39 * @param <T> the type of objects that this object may be differentiated against
40 * @since 3.3
41 */
42 @FunctionalInterface
43 public interface Diffable<T> {
44
45 /**
46 * Retrieves a list of the differences between
47 * this object and the supplied object.
48 *
49 * @param obj the object to diff against, can be {@code null}
50 * @return a list of differences
51 * @throws NullPointerException if the specified object is {@code null}
52 */
53 DiffResult<T> diff(T obj);
54 }