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/*
* Copyright (C) 2007 The Guava Authors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.common.collect;
import com.google.common.annotations.GwtCompatible;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import com.google.errorprone.annotations.DoNotMock;
import java.util.Map;
import javax.annotation.CheckForNull;
/**
* A map, each entry of which maps a Java raw type to an
* instance of that type. In addition to implementing {@code Map}, the additional type-safe
* operations {@link #putInstance} and {@link #getInstance} are available.
*
* Like any other {@code Map}, this map may contain entries for primitive types,
* and a primitive type and its corresponding wrapper type may map to different values.
*
* This class's support for {@code null} requires some explanation: From release 31.0 onward,
* Guava specifies the nullness of its types through annotations. In the case of {@code
* ClassToInstanceMap}, it specifies that both the key and value types are restricted to
* non-nullable types. This specification is reasonable for keys, which must be non-null
* classes. This is in contrast to the specification for values: Null values are
* supported by the implementation {@link MutableClassToInstanceMap}, even though that
* implementation and this interface specify otherwise. Thus, if you use a nullness checker, you can
* safely suppress any warnings it produces when you write null values into a {@code
* MutableClassToInstanceMap}. Just be sure to be prepared for null values when reading from it,
* since nullness checkers will assume that vaules are non-null then, too.
*
*
See the Guava User Guide article on {@code
* ClassToInstanceMap}.
*
*
To map a generic type to an instance of that type, use {@link
* com.google.common.reflect.TypeToInstanceMap} instead.
*
* @param the common supertype that all entries must share; often this is simply {@link Object}
* @author Kevin Bourrillion
* @since 2.0
*/
@DoNotMock("Use ImmutableClassToInstanceMap or MutableClassToInstanceMap")
@GwtCompatible
@ElementTypesAreNonnullByDefault
// If we ever support non-null projections (https://github.com/jspecify/jspecify/issues/86), we
// we might annotate this as...
// ClassToInstanceMap extends Map, B>
// ...and change its methods similarly ( or Class<@Nonnull T>).
public interface ClassToInstanceMap extends Map, B> {
/**
* Returns the value the specified class is mapped to, or {@code null} if no entry for this class
* is present. This will only return a value that was bound to this specific class, not a value
* that may have been bound to a subtype.
*/
@CheckForNull
T getInstance(Class type);
/**
* Maps the specified class to the specified value. Does not associate this value with any
* of the class's supertypes.
*
* @return the value previously associated with this class (possibly {@code null}), or {@code
* null} if there was no previous entry.
*/
@CanIgnoreReturnValue
@CheckForNull
T putInstance(Class type, T value);
}