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;
020
021import java.util.Map;
022
023import javax.annotation.Nullable;
024
025/**
026 * A map, each entry of which maps a Java
027 * <a href="http://tinyurl.com/2cmwkz">raw type</a> to an instance of that type.
028 * In addition to implementing {@code Map}, the additional type-safe operations
029 * {@link #putInstance} and {@link #getInstance} are available.
030 *
031 * <p>Like any other {@code Map<Class, Object>}, this map may contain entries
032 * for primitive types, and a primitive type and its corresponding wrapper type
033 * may map to different values.
034 * 
035 * <p>See the Guava User Guide article on <a href=
036 * "http://code.google.com/p/guava-libraries/wiki/NewCollectionTypesExplained#ClassToInstanceMap">
037 * {@code 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 entries must share; often this is
043 *     simply {@link Object}
044 *
045 * @author Kevin Bourrillion
046 * @since 2.0 (imported from Google Collections Library)
047 */
048@GwtCompatible
049public interface ClassToInstanceMap<B> extends Map<Class<? extends B>, B> {
050  /**
051   * Returns the value the specified class is mapped to, or {@code null} if no
052   * entry for this class is present. This will only return a value that was
053   * bound to this specific class, not a value that may have been bound to a
054   * subtype.
055   */
056  <T extends B> T getInstance(Class<T> type);
057
058  /**
059   * Maps the specified class to the specified value. Does <i>not</i> associate
060   * this value with any of the class's supertypes.
061   *
062   * @return the value previously associated with this class (possibly {@code
063   *     null}), or {@code null} if there was no previous entry.
064   */
065  <T extends B> T putInstance(Class<T> type, @Nullable T value);
066}