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