001    /*
002     * Copyright (C) 2007 Google Inc.
003     *
004     * Licensed under the Apache License, Version 2.0 (the "License");
005     * you may not use this file except in compliance with the License.
006     * You may obtain a copy of the License at
007     *
008     * http://www.apache.org/licenses/LICENSE-2.0
009     *
010     * Unless required by applicable law or agreed to in writing, software
011     * distributed under the License is distributed on an "AS IS" BASIS,
012     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013     * See the License for the specific language governing permissions and
014     * limitations under the License.
015     */
016    
017    package com.google.common.collect;
018    
019    import com.google.common.annotations.GwtCompatible;
020    
021    import java.util.Map;
022    
023    import javax.annotation.Nullable;
024    
025    /**
026     * An object representing the differences between two maps.
027     *
028     * @author Kevin Bourrillion
029     * @since 2 (imported from Google Collections Library)
030     */
031    @GwtCompatible
032    public interface MapDifference<K, V> {
033      /**
034       * Returns {@code true} if there are no differences between the two maps;
035       * that is, if the maps are equal.
036       */
037      boolean areEqual();
038    
039      /**
040       * Returns an unmodifiable map containing the entries from the left map whose
041       * keys are not present in the right map.
042       */
043      Map<K, V> entriesOnlyOnLeft();
044    
045      /**
046       * Returns an unmodifiable map containing the entries from the right map whose
047       * keys are not present in the left map.
048       */
049      Map<K, V> entriesOnlyOnRight();
050    
051      /**
052       * Returns an unmodifiable map containing the entries that appear in both
053       * maps; that is, the intersection of the two maps.
054       */
055      Map<K, V> entriesInCommon();
056    
057      /**
058       * Returns an unmodifiable map describing keys that appear in both maps, but
059       * with different values.
060       */
061      Map<K, ValueDifference<V>> entriesDiffering();
062    
063      /**
064       * Compares the specified object with this instance for equality. Returns
065       * {@code true} if the given object is also a {@code MapDifference} and the
066       * values returned by the {@link #entriesOnlyOnLeft()}, {@link
067       * #entriesOnlyOnRight()}, {@link #entriesInCommon()} and {@link
068       * #entriesDiffering()} of the two instances are equal.
069       */
070      boolean equals(@Nullable Object object);
071    
072      /**
073       * Returns the hash code for this instance. This is defined as the hash code
074       * of <pre>   {@code
075       *
076       *   Arrays.asList(entriesOnlyOnLeft(), entriesOnlyOnRight(),
077       *       entriesInCommon(), entriesDiffering())}</pre>
078       */
079      int hashCode();
080    
081      /**
082       * A difference between the mappings from two maps with the same key. The
083       * {@code leftValue()} and {@code rightValue} are not equal, and one but not
084       * both of them may be null.
085       */
086      interface ValueDifference<V> {
087        /**
088         * Returns the value from the left map (possibly null).
089         */
090        V leftValue();
091    
092        /**
093         * Returns the value from the right map (possibly null).
094         */
095        V rightValue();
096    
097        /**
098         * Two instances are considered equal if their {@link #leftValue()}
099         * values are equal and their {@link #rightValue()} values are also equal.
100         */
101        @Override boolean equals(@Nullable Object other);
102    
103        /**
104         * The hash code equals the value
105         * {@code Arrays.asList(leftValue(), rightValue()).hashCode()}.
106         */
107        @Override int hashCode();
108      }
109    
110    }