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 javax.annotation.CheckForNull;
024import org.checkerframework.checker.nullness.qual.NonNull;
025import org.checkerframework.checker.nullness.qual.Nullable;
026
027/**
028 * A map, each entry of which maps a Java <a href="http://tinyurl.com/2cmwkz">raw type</a> to an
029 * instance of that type. In addition to implementing {@code Map}, the additional type-safe
030 * operations {@link #putInstance} and {@link #getInstance} are available.
031 *
032 * <p>Like any other {@code Map<Class, Object>}, this map may contain entries for primitive types,
033 * and a primitive type and its corresponding wrapper type may map to different values.
034 *
035 * <h3>Implementations</h3>
036 *
037 * <ul>
038 *   <li>{@link ImmutableClassToInstanceMap}
039 *   <li>{@link MutableClassToInstanceMap}
040 * </ul>
041 *
042 * <p>To map a generic type to an instance of that type, use {@link
043 * com.google.common.reflect.TypeToInstanceMap} instead.
044 *
045 * <p>See the Guava User Guide article on <a href=
046 * "https://github.com/google/guava/wiki/NewCollectionTypesExplained#classtoinstancemap">{@code
047 * ClassToInstanceMap}</a>.
048 *
049 * @param <B> the common supertype that all values will share. When in doubt, just use {@link
050 *     Object}, or use {@code @Nullable Object} to allow null values.
051 * @since 2.0
052 */
053@DoNotMock("Use ImmutableClassToInstanceMap or MutableClassToInstanceMap")
054@GwtCompatible
055@ElementTypesAreNonnullByDefault
056public interface ClassToInstanceMap<B extends @Nullable Object>
057    extends Map<Class<? extends @NonNull B>, B> {
058  /**
059   * Returns the value the specified class is mapped to, or {@code null} if no entry for this class
060   * is present. This will only return a value that was bound to this specific class, not a value
061   * that may have been bound to a subtype.
062   */
063  @CheckForNull
064  <T extends @NonNull B> T getInstance(Class<T> type);
065
066  /**
067   * Maps the specified class to the specified value. Does <i>not</i> associate this value with any
068   * of the class's supertypes.
069   *
070   * @return the value previously associated with this class (possibly {@code null}), or {@code
071   *     null} if there was no previous entry.
072   */
073  @CanIgnoreReturnValue
074  @CheckForNull
075  <T extends B> T putInstance(Class<@NonNull T> type, @ParametricNullness T value);
076}