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 java.util.Map;
022import org.checkerframework.checker.nullness.compatqual.NullableDecl;
023
024/**
025 * A map, each entry of which maps a Java <a href="http://tinyurl.com/2cmwkz">raw type</a> to an
026 * instance of that type. In addition to implementing {@code Map}, the additional type-safe
027 * operations {@link #putInstance} and {@link #getInstance} are available.
028 *
029 * <p>Like any other {@code Map<Class, Object>}, this map may contain entries for primitive types,
030 * and a primitive type and its corresponding wrapper type may map to different values.
031 *
032 * <p>See the Guava User Guide article on <a href=
033 * "https://github.com/google/guava/wiki/NewCollectionTypesExplained#classtoinstancemap"> {@code
034 * ClassToInstanceMap}</a>.
035 *
036 * <p>To map a generic type to an instance of that type, use {@link
037 * com.google.common.reflect.TypeToInstanceMap} instead.
038 *
039 * @param <B> the common supertype that all entries must share; often this is simply {@link Object}
040 * @author Kevin Bourrillion
041 * @since 2.0
042 */
043@GwtCompatible
044public interface ClassToInstanceMap<B> extends Map<Class<? extends B>, B> {
045  /**
046   * Returns the value the specified class is mapped to, or {@code null} if no entry for this class
047   * is present. This will only return a value that was bound to this specific class, not a value
048   * that may have been bound to a subtype.
049   */
050  @CanIgnoreReturnValue // TODO(kak): Consider removing this?
051  <T extends B> T getInstance(Class<T> type);
052
053  /**
054   * Maps the specified class to the specified value. Does <i>not</i> associate this value with any
055   * of the class's supertypes.
056   *
057   * @return the value previously associated with this class (possibly {@code null}), or {@code
058   *     null} if there was no previous entry.
059   */
060  @CanIgnoreReturnValue
061  <T extends B> T putInstance(Class<T> type, @NullableDecl T value);
062}