1   /*
2    * Copyright (C) 2007 The Guava Authors
3    *
4    * Licensed under the Apache License, Version 2.0 (the "License");
5    * you may not use this file except in compliance with the License.
6    * You may obtain a copy of the License at
7    *
8    * http://www.apache.org/licenses/LICENSE-2.0
9    *
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS,
12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13   * See the License for the specific language governing permissions and
14   * limitations under the License.
15   */
16  
17  package com.google.common.collect;
18  
19  import com.google.common.annotations.GwtCompatible;
20  
21  import java.util.Map;
22  
23  import javax.annotation.Nullable;
24  
25  /**
26   * A map, each entry of which maps a Java
27   * <a href="http://tinyurl.com/2cmwkz">raw type</a> to an instance of that type.
28   * In addition to implementing {@code Map}, the additional type-safe operations
29   * {@link #putInstance} and {@link #getInstance} are available.
30   *
31   * <p>Like any other {@code Map<Class, Object>}, this map may contain entries
32   * for primitive types, and a primitive type and its corresponding wrapper type
33   * may map to different values.
34   * 
35   * <p>See the Guava User Guide article on <a href=
36   * "http://code.google.com/p/guava-libraries/wiki/NewCollectionTypesExplained#ClassToInstanceMap">
37   * {@code ClassToInstanceMap}</a>.
38   *
39   * <p>To map a generic type to an instance of that type, use {@link
40   * com.google.common.reflect.TypeToInstanceMap} instead.
41   *
42   * @param <B> the common supertype that all entries must share; often this is
43   *     simply {@link Object}
44   *
45   * @author Kevin Bourrillion
46   * @since 2.0 (imported from Google Collections Library)
47   */
48  @GwtCompatible
49  public interface ClassToInstanceMap<B> extends Map<Class<? extends B>, B> {
50    /**
51     * Returns the value the specified class is mapped to, or {@code null} if no
52     * entry for this class is present. This will only return a value that was
53     * bound to this specific class, not a value that may have been bound to a
54     * subtype.
55     */
56    <T extends B> T getInstance(Class<T> type);
57  
58    /**
59     * Maps the specified class to the specified value. Does <i>not</i> associate
60     * this value with any of the class's supertypes.
61     *
62     * @return the value previously associated with this class (possibly {@code
63     *     null}), or {@code null} if there was no previous entry.
64     */
65    <T extends B> T putInstance(Class<T> type, @Nullable T value);
66  }