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
017package com.google.common.collect;
018
019import com.google.common.annotations.GwtCompatible;
020import com.google.errorprone.annotations.CanIgnoreReturnValue;
021import com.google.errorprone.annotations.DoNotMock;
022import java.util.Map;
023import org.jspecify.annotations.NonNull;
024import org.jspecify.annotations.Nullable;
025
026/**
027 * A map, each entry of which maps a Java <a href="http://tinyurl.com/2cmwkz">raw type</a> to an
028 * instance of that type. In addition to implementing {@code Map}, the additional type-safe
029 * operations {@link #putInstance} and {@link #getInstance} are available.
030 *
031 * <p>Like any other {@code Map<Class, Object>}, this map may contain entries for primitive types,
032 * and a primitive type and its corresponding wrapper type may map to different values.
033 *
034 * <h3>Implementations</h3>
035 *
036 * <ul>
037 *   <li>{@link ImmutableClassToInstanceMap}
038 *   <li>{@link MutableClassToInstanceMap}
039 * </ul>
040 *
041 * <p>To map a generic type to an instance of that type, use {@link
042 * com.google.common.reflect.TypeToInstanceMap} instead.
043 *
044 * <p>See the Guava User Guide article on <a href=
045 * "https://github.com/google/guava/wiki/NewCollectionTypesExplained#classtoinstancemap">{@code
046 * ClassToInstanceMap}</a>.
047 *
048 * @param <B> the common supertype that all values will share. When in doubt, just use {@link
049 *     Object}, or use {@code @Nullable Object} to allow null values.
050 * @since 2.0
051 */
052@DoNotMock("Use ImmutableClassToInstanceMap or MutableClassToInstanceMap")
053@GwtCompatible
054public interface ClassToInstanceMap<B extends @Nullable Object>
055    extends Map<Class<? extends @NonNull B>, B> {
056  /**
057   * Returns the value the specified class is mapped to, or {@code null} if no entry for this class
058   * is present. This will only return a value that was bound to this specific class, not a value
059   * that may have been bound to a subtype.
060   */
061  <T extends @NonNull B> @Nullable T getInstance(Class<T> type);
062
063  /**
064   * Maps the specified class to the specified value. Does <i>not</i> associate this value with any
065   * of the class's supertypes.
066   *
067   * @return the value previously associated with this class (possibly {@code null}), or {@code
068   *     null} if there was no previous entry.
069   */
070  @CanIgnoreReturnValue
071  <T extends B> @Nullable T putInstance(Class<@NonNull T> type, @ParametricNullness T value);
072}