com.google.common.reflect.TypeToInstanceMap Maven / Gradle / Ivy

Show more of this group Show more artifacts with this name
Show all versions of guava Show documentation

Guava is a suite of core and expanded libraries that include utility classes, google's collections, io classes, and much much more.

There is a newer version: 33.1.0-jre

Show newest version

/*
 * Copyright (C) 2012 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.reflect;

import com.google.common.annotations.Beta;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import java.util.Map;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * A map, each entry of which maps a {@link TypeToken} to an instance of that type. In addition to
 * implementing {@code Map}, the additional type-safe operations {@link #putInstance} and {@link
 * #getInstance} are available.
 *
 * Generally, implementations don't support {@link #put} and {@link #putAll} because there is no
 * way to check an object at runtime to be an instance of a {@link TypeToken}. Instead, caller
 * should use the type safe {@link #putInstance}.
 *
 * 
Also, if caller suppresses unchecked warnings and passes in an {@code Iterable} for
 * type {@code Iterable}, the map won't be able to detect and throw type error.
 *
 * 
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.
 *
 * @param  the common supertype that all entries must share; often this is simply {@link Object}
 * @author Ben Yu
 * @since 13.0
 */
@Beta
public interface TypeToInstanceMap 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.
   *
   * 
{@code getInstance(Foo.class)} is equivalent to {@code
   * getInstance(TypeToken.of(Foo.class))}.
   */
   @Nullable T getInstance(Class type);

  /**
   * Returns the value the specified type is mapped to, or {@code null} if no entry for this type is
   * present. This will only return a value that was bound to this specific type, not a value that
   * may have been bound to a subtype.
   */
   @Nullable T getInstance(TypeToken type);

  /**
   * Maps the specified class to the specified value. Does not associate this value with any
   * of the class's supertypes.
   *
   * {@code putInstance(Foo.class, foo)} is equivalent to {@code
   * putInstance(TypeToken.of(Foo.class), foo)}.
   *
   * @return the value previously associated with this class (possibly {@code null}), or {@code
   *     null} if there was no previous entry.
   */
  @CanIgnoreReturnValue
   @Nullable T putInstance(Class type, @Nullable T value);

  /**
   * Maps the specified type to the specified value. Does not associate this value with any
   * of the type's supertypes.
   *
   * @return the value previously associated with this type (possibly {@code null}), or {@code null}
   *     if there was no previous entry.
   */
  @CanIgnoreReturnValue
   @Nullable T putInstance(TypeToken type, @Nullable T value);
}