1/*
2 * Copyright (C) 2007 The Guava Authors
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package com.google.common.collect;
18
19import com.google.common.annotations.GwtCompatible;
20
21import java.util.Map;
22
23import javax.annotation.Nullable;
24
25/**
26 * An object representing the differences between two maps.
27 *
28 * @author Kevin Bourrillion
29 * @since 2.0 (imported from Google Collections Library)
30 */
31@GwtCompatible
32public interface MapDifference<K, V> {
33  /**
34   * Returns {@code true} if there are no differences between the two maps;
35   * that is, if the maps are equal.
36   */
37  boolean areEqual();
38
39  /**
40   * Returns an unmodifiable map containing the entries from the left map whose
41   * keys are not present in the right map.
42   */
43  Map<K, V> entriesOnlyOnLeft();
44
45  /**
46   * Returns an unmodifiable map containing the entries from the right map whose
47   * keys are not present in the left map.
48   */
49  Map<K, V> entriesOnlyOnRight();
50
51  /**
52   * Returns an unmodifiable map containing the entries that appear in both
53   * maps; that is, the intersection of the two maps.
54   */
55  Map<K, V> entriesInCommon();
56
57  /**
58   * Returns an unmodifiable map describing keys that appear in both maps, but
59   * with different values.
60   */
61  Map<K, ValueDifference<V>> entriesDiffering();
62
63  /**
64   * Compares the specified object with this instance for equality. Returns
65   * {@code true} if the given object is also a {@code MapDifference} and the
66   * values returned by the {@link #entriesOnlyOnLeft()}, {@link
67   * #entriesOnlyOnRight()}, {@link #entriesInCommon()} and {@link
68   * #entriesDiffering()} of the two instances are equal.
69   */
70  @Override
71  boolean equals(@Nullable Object object);
72
73  /**
74   * Returns the hash code for this instance. This is defined as the hash code
75   * of <pre>   {@code
76   *
77   *   Arrays.asList(entriesOnlyOnLeft(), entriesOnlyOnRight(),
78   *       entriesInCommon(), entriesDiffering())}</pre>
79   */
80  @Override
81  int hashCode();
82
83  /**
84   * A difference between the mappings from two maps with the same key. The
85   * {@link #leftValue} and {@link #rightValue} are not equal, and one but not
86   * both of them may be null.
87   *
88   * @since 2.0 (imported from Google Collections Library)
89   */
90  interface ValueDifference<V> {
91    /**
92     * Returns the value from the left map (possibly null).
93     */
94    V leftValue();
95
96    /**
97     * Returns the value from the right map (possibly null).
98     */
99    V rightValue();
100
101    /**
102     * Two instances are considered equal if their {@link #leftValue()}
103     * values are equal and their {@link #rightValue()} values are also equal.
104     */
105    @Override boolean equals(@Nullable Object other);
106
107    /**
108     * The hash code equals the value
109     * {@code Arrays.asList(leftValue(), rightValue()).hashCode()}.
110     */
111    @Override int hashCode();
112  }
113
114}
115