    001    /*
    002     * Copyright (C) 2007 The Guava Authors
    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 2.0 (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      @Override
    071      boolean equals(@Nullable Object object);
    072
    073      /**
    074       * Returns the hash code for this instance. This is defined as the hash code
    075       * of <pre>   {@code
    076       *
    077       *   Arrays.asList(entriesOnlyOnLeft(), entriesOnlyOnRight(),
    078       *       entriesInCommon(), entriesDiffering())}</pre>
    079       */
    080      @Override
    081      int hashCode();
    082
    083      /**
    084       * A difference between the mappings from two maps with the same key. The
    085       * {@link #leftValue} and {@link #rightValue} are not equal, and one but not
    086       * both of them may be null.
    087       *
    088       * @since 2.0 (imported from Google Collections Library)
    089       */
    090      interface ValueDifference<V> {
    091        /**
    092         * Returns the value from the left map (possibly null).
    093         */
    094        V leftValue();
    095
    096        /**
    097         * Returns the value from the right map (possibly null).
    098         */
    099        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    }