com.google.common.collect.BiMap.java Source code

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Here is the source code for com.google.common.collect.BiMap.java

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/*
 * Copyright (C) 2007 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.collect;

import com.google.common.annotations.GwtCompatible;

import java.util.Map;
import java.util.Set;

import javax.annotation.Nullable;

/**
 * A bimap (or "bidirectional map") is a map that preserves the uniqueness of
 * its values as well as that of its keys. This constraint enables bimaps to
 * support an "inverse view", which is another bimap containing the same entries
 * as this bimap but with reversed keys and values.
 *
 * <p>See the Guava User Guide article on <a href=
 * "https://github.com/google/guava/wiki/NewCollectionTypesExplained#bimap">
 * {@code BiMap}</a>.
 *
 * @author Kevin Bourrillion
 * @since 2.0
 */
@GwtCompatible
public interface BiMap<K, V> extends Map<K, V> {
    // Modification Operations

    /**
     * {@inheritDoc}
     *
     * @throws IllegalArgumentException if the given value is already bound to a
     *     different key in this bimap. The bimap will remain unmodified in this
     *     event. To avoid this exception, call {@link #forcePut} instead.
     */
    @Override
    @Nullable
    V put(@Nullable K key, @Nullable V value);

    /**
     * An alternate form of {@code put} that silently removes any existing entry
     * with the value {@code value} before proceeding with the {@link #put}
     * operation. If the bimap previously contained the provided key-value
     * mapping, this method has no effect.
     *
     * <p>Note that a successful call to this method could cause the size of the
     * bimap to increase by one, stay the same, or even decrease by one.
     *
     * <p><b>Warning:</b> If an existing entry with this value is removed, the key
     * for that entry is discarded and not returned.
     *
     * @param key the key with which the specified value is to be associated
     * @param value the value to be associated with the specified key
     * @return the value which was previously associated with the key, which may
     *     be {@code null}, or {@code null} if there was no previous entry
     */
    @Nullable
    V forcePut(@Nullable K key, @Nullable V value);

    // Bulk Operations

    /**
     * {@inheritDoc}
     *
     * <p><b>Warning:</b> the results of calling this method may vary depending on
     * the iteration order of {@code map}.
     *
     * @throws IllegalArgumentException if an attempt to {@code put} any
     *     entry fails. Note that some map entries may have been added to the
     *     bimap before the exception was thrown.
     */
    @Override
    void putAll(Map<? extends K, ? extends V> map);

    // Views

    /**
     * {@inheritDoc}
     *
     * <p>Because a bimap has unique values, this method returns a {@link Set},
     * instead of the {@link java.util.Collection} specified in the {@link Map}
     * interface.
     */
    @Override
    Set<V> values();

    /**
     * Returns the inverse view of this bimap, which maps each of this bimap's
     * values to its associated key. The two bimaps are backed by the same data;
     * any changes to one will appear in the other.
     *
     * <p><b>Note:</b>There is no guaranteed correspondence between the iteration
     * order of a bimap and that of its inverse.
     *
     * @return the inverse view of this bimap
     */
    BiMap<V, K> inverse();
}