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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    
017    package com.google.common.collect;
018    
019    import com.google.common.annotations.GwtCompatible;
020    
021    import java.util.Map;
022    
023    import 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     * @param <B> the common supertype that all entries must share; often this is
036     *     simply {@link Object}
037     *
038     * @author Kevin Bourrillion
039     * @since 2.0 (imported from Google Collections Library)
040     */
041    @GwtCompatible
042    public interface ClassToInstanceMap<B> extends Map<Class<? extends B>, B> {
043      /**
044       * Returns the value the specified class is mapped to, or {@code null} if no
045       * entry for this class is present. This will only return a value that was
046       * bound to this specific class, not a value that may have been bound to a
047       * subtype.
048       */
049      <T extends B> T getInstance(Class<T> type);
050    
051      /**
052       * Maps the specified class to the specified value. Does <i>not</i> associate
053       * this value with any of the class's supertypes.
054       *
055       * @return the value previously associated with this class (possibly {@code
056       *     null}), or {@code null} if there was no previous entry.
057       */
058      <T extends B> T putInstance(Class<T> type, @Nullable T value);
059    }