001/*
002 * Copyright (C) 2009 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 static com.google.common.base.Preconditions.checkNotNull;
020
021import com.google.common.annotations.GwtIncompatible;
022import com.google.common.primitives.Primitives;
023import com.google.errorprone.annotations.CanIgnoreReturnValue;
024import com.google.errorprone.annotations.DoNotCall;
025import com.google.errorprone.annotations.Immutable;
026import java.io.Serializable;
027import java.util.Map;
028import javax.annotation.CheckForNull;
029import org.checkerframework.checker.nullness.qual.NonNull;
030
031/**
032 * A {@link ClassToInstanceMap} whose contents will never change, with many other important
033 * properties detailed at {@link ImmutableCollection}.
034 *
035 * @author Kevin Bourrillion
036 * @since 2.0
037 */
038@Immutable(containerOf = "B")
039@GwtIncompatible
040@ElementTypesAreNonnullByDefault
041// TODO(b/278589132): Remove the redundant "@NonNull" on B once it's no longer required by J2KT.
042public final class ImmutableClassToInstanceMap<B>
043    extends ForwardingMap<Class<? extends @NonNull B>, B>
044    implements ClassToInstanceMap<B>, Serializable {
045
046  private static final ImmutableClassToInstanceMap<Object> EMPTY =
047      new ImmutableClassToInstanceMap<>(ImmutableMap.<Class<?>, Object>of());
048
049  /**
050   * Returns an empty {@code ImmutableClassToInstanceMap}.
051   *
052   * <p><b>Performance note:</b> the instance returned is a singleton.
053   *
054   * @since 19.0
055   */
056  @SuppressWarnings("unchecked")
057  public static <B> ImmutableClassToInstanceMap<B> of() {
058    return (ImmutableClassToInstanceMap<B>) EMPTY;
059  }
060
061  /**
062   * Returns an {@code ImmutableClassToInstanceMap} containing a single entry.
063   *
064   * @since 19.0
065   */
066  public static <B, T extends B> ImmutableClassToInstanceMap<B> of(Class<T> type, T value) {
067    ImmutableMap<Class<? extends B>, B> map = ImmutableMap.<Class<? extends B>, B>of(type, value);
068    return new ImmutableClassToInstanceMap<>(map);
069  }
070
071  /**
072   * Returns a new builder. The generated builder is equivalent to the builder created by the {@link
073   * Builder} constructor.
074   */
075  public static <B> Builder<B> builder() {
076    return new Builder<>();
077  }
078
079  /**
080   * A builder for creating immutable class-to-instance maps. Example:
081   *
082   * <pre>{@code
083   * static final ImmutableClassToInstanceMap<Handler> HANDLERS =
084   *     new ImmutableClassToInstanceMap.Builder<Handler>()
085   *         .put(FooHandler.class, new FooHandler())
086   *         .put(BarHandler.class, new SubBarHandler())
087   *         .put(Handler.class, new QuuxHandler())
088   *         .build();
089   * }</pre>
090   *
091   * <p>After invoking {@link #build()} it is still possible to add more entries and build again.
092   * Thus each map generated by this builder will be a superset of any map generated before it.
093   *
094   * @since 2.0
095   */
096  public static final class Builder<B> {
097    private final ImmutableMap.Builder<Class<? extends B>, B> mapBuilder = ImmutableMap.builder();
098
099    /**
100     * Associates {@code key} with {@code value} in the built map. Duplicate keys are not allowed,
101     * and will cause {@link #build} to fail.
102     */
103    @CanIgnoreReturnValue
104    public <T extends B> Builder<B> put(Class<T> key, T value) {
105      mapBuilder.put(key, value);
106      return this;
107    }
108
109    /**
110     * Associates all of {@code map's} keys and values in the built map. Duplicate keys are not
111     * allowed, and will cause {@link #build} to fail.
112     *
113     * @throws NullPointerException if any key or value in {@code map} is null
114     * @throws ClassCastException if any value is not an instance of the type specified by its key
115     */
116    @CanIgnoreReturnValue
117    public <T extends B> Builder<B> putAll(Map<? extends Class<? extends T>, ? extends T> map) {
118      for (Entry<? extends Class<? extends T>, ? extends T> entry : map.entrySet()) {
119        Class<? extends T> type = entry.getKey();
120        T value = entry.getValue();
121        mapBuilder.put(type, cast(type, value));
122      }
123      return this;
124    }
125
126    private static <T> T cast(Class<T> type, Object value) {
127      return Primitives.wrap(type).cast(value);
128    }
129
130    /**
131     * Returns a new immutable class-to-instance map containing the entries provided to this
132     * builder.
133     *
134     * @throws IllegalArgumentException if duplicate keys were added
135     */
136    public ImmutableClassToInstanceMap<B> build() {
137      ImmutableMap<Class<? extends B>, B> map = mapBuilder.buildOrThrow();
138      if (map.isEmpty()) {
139        return of();
140      } else {
141        return new ImmutableClassToInstanceMap<>(map);
142      }
143    }
144  }
145
146  /**
147   * Returns an immutable map containing the same entries as {@code map}. If {@code map} somehow
148   * contains entries with duplicate keys (for example, if it is a {@code SortedMap} whose
149   * comparator is not <i>consistent with equals</i>), the results of this method are undefined.
150   *
151   * <p><b>Note:</b> Despite what the method name suggests, if {@code map} is an {@code
152   * ImmutableClassToInstanceMap}, no copy will actually be performed.
153   *
154   * @throws NullPointerException if any key or value in {@code map} is null
155   * @throws ClassCastException if any value is not an instance of the type specified by its key
156   */
157  public static <B, S extends B> ImmutableClassToInstanceMap<B> copyOf(
158      Map<? extends Class<? extends S>, ? extends S> map) {
159    if (map instanceof ImmutableClassToInstanceMap) {
160      @SuppressWarnings("rawtypes") // JDT-based J2KT Java frontend does not permit the direct cast
161      Map rawMap = map;
162      @SuppressWarnings("unchecked") // covariant casts safe (unmodifiable)
163      ImmutableClassToInstanceMap<B> cast = (ImmutableClassToInstanceMap<B>) rawMap;
164      return cast;
165    }
166    return new Builder<B>().putAll(map).build();
167  }
168
169  private final ImmutableMap<Class<? extends B>, B> delegate;
170
171  private ImmutableClassToInstanceMap(ImmutableMap<Class<? extends B>, B> delegate) {
172    this.delegate = delegate;
173  }
174
175  @Override
176  protected Map<Class<? extends B>, B> delegate() {
177    return delegate;
178  }
179
180  @Override
181  @SuppressWarnings("unchecked") // value could not get in if not a T
182  @CheckForNull
183  public <T extends B> T getInstance(Class<T> type) {
184    return (T) delegate.get(checkNotNull(type));
185  }
186
187  /**
188   * Guaranteed to throw an exception and leave the map unmodified.
189   *
190   * @throws UnsupportedOperationException always
191   * @deprecated Unsupported operation.
192   */
193  @CanIgnoreReturnValue
194  @Deprecated
195  @Override
196  @DoNotCall("Always throws UnsupportedOperationException")
197  @CheckForNull
198  public <T extends B> T putInstance(Class<T> type, T value) {
199    throw new UnsupportedOperationException();
200  }
201
202  Object readResolve() {
203    return isEmpty() ? of() : this;
204  }
205}