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