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 * <p>See the Guava User Guide article on <a href=
036 * "https://github.com/google/guava/wiki/NewCollectionTypesExplained#classtoinstancemap">{@code
037 * ClassToInstanceMap}</a>.
038 *
039 * <p>To map a generic type to an instance of that type, use {@link
040 * com.google.common.reflect.TypeToInstanceMap} instead.
041 *
042 * @param <B> the common supertype that all values will share. When in doubt, just use {@link
043 *     Object}, or use {@code @Nullable Object} to allow null values.
044 * @since 2.0
045 */
046@DoNotMock("Use ImmutableClassToInstanceMap or MutableClassToInstanceMap")
047@GwtCompatible
048@ElementTypesAreNonnullByDefault
049public interface ClassToInstanceMap<B extends @Nullable Object>
050    extends Map<Class<? extends @NonNull B>, B> {
051  /**
052   * Returns the value the specified class is mapped to, or {@code null} if no entry for this class
053   * is present. This will only return a value that was bound to this specific class, not a value
054   * that may have been bound to a subtype.
055   */
056  @CheckForNull
057  <T extends @NonNull B> T getInstance(Class<T> type);
058
059  /**
060   * Maps the specified class to the specified value. Does <i>not</i> associate this value with any
061   * of the class's supertypes.
062   *
063   * @return the value previously associated with this class (possibly {@code null}), or {@code
064   *     null} if there was no previous entry.
065   */
066  @CanIgnoreReturnValue
067  @CheckForNull
068  <T extends B> T putInstance(Class<@NonNull T> type, @ParametricNullness T value);
069}