Java example source code file (ImmutableClassToInstanceMap.java)

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Java - Java tags/keywords

annotation, builder, canignorereturnvalue, deprecated, empty, forwardingmap, gwtincompatible, immutableclasstoinstancemap, immutablemap, object, override, serializable, suppresswarnings, util

The ImmutableClassToInstanceMap.java Java example source code

/*
 * Copyright (C) 2009 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 static com.google.common.base.Preconditions.checkNotNull;

import com.google.common.annotations.GwtIncompatible;
import com.google.common.primitives.Primitives;
import com.google.errorprone.annotations.CanIgnoreReturnValue;

import java.io.Serializable;
import java.util.Map;

import javax.annotation.Nullable;

/**
 * A {@link ClassToInstanceMap} whose contents will never change, with many
 * other important properties detailed at {@link ImmutableCollection}.
 *
 * @author Kevin Bourrillion
 * @since 2.0
 */
@GwtIncompatible
public final class ImmutableClassToInstanceMap<B> extends ForwardingMap, B>
    implements ClassToInstanceMap<B>, Serializable {

  private static final ImmutableClassToInstanceMap<Object> EMPTY =
      new ImmutableClassToInstanceMap<Object>(ImmutableMap., Object>of());

  /**
   * Returns an empty {@code ImmutableClassToInstanceMap}.
   *
   * @since 19.0
   */
  @SuppressWarnings("unchecked")
  public static <B> ImmutableClassToInstanceMap of() {
    return (ImmutableClassToInstanceMap<B>) EMPTY;
  }

  /**
   * Returns an {@code ImmutableClassToInstanceMap} containing a single entry.
   *
   * @since 19.0
   */
  public static <B, T extends B> ImmutableClassToInstanceMap of(Class type, T value) {
    ImmutableMap<Class map = ImmutableMap., B>of(type, value);
    return new ImmutableClassToInstanceMap<B>(map);
  }

  /**
   * Returns a new builder. The generated builder is equivalent to the builder
   * created by the {@link Builder} constructor.
   */
  public static <B> Builder builder() {
    return new Builder<B>();
  }

  /**
   * A builder for creating immutable class-to-instance maps. Example:
   * <pre>   {@code
   *
   *   static final ImmutableClassToInstanceMap<Handler> HANDLERS =
   *       new ImmutableClassToInstanceMap.Builder<Handler>()
   *           .put(FooHandler.class, new FooHandler())
   *           .put(BarHandler.class, new SubBarHandler())
   *           .put(Handler.class, new QuuxHandler())
   *           .build();}</pre>
   *
   * <p>After invoking {@link #build()} it is still possible to add more entries
   * and build again. Thus each map generated by this builder will be a superset
   * of any map generated before it.
   *
   * @since 2.0
   */
  public static final class Builder<B> {
    private final ImmutableMap.Builder<Class mapBuilder = ImmutableMap.builder();

    /**
     * Associates {@code key} with {@code value} in the built map. Duplicate
     * keys are not allowed, and will cause {@link #build} to fail.
     */
    @CanIgnoreReturnValue
    public <T extends B> Builder put(Class key, T value) {
      mapBuilder.put(key, value);
      return this;
    }

    /**
     * Associates all of {@code map's} keys and values in the built map.
     * Duplicate keys are not allowed, and will cause {@link #build} to fail.
     *
     * @throws NullPointerException if any key or value in {@code map} is null
     * @throws ClassCastException if any value is not an instance of the type
     *     specified by its key
     */
    @CanIgnoreReturnValue
    public <T extends B> Builder putAll(Map, ? extends T> map) {
      for (Entry<? extends Class entry : map.entrySet()) {
        Class<? extends T> type = entry.getKey();
        T value = entry.getValue();
        mapBuilder.put(type, cast(type, value));
      }
      return this;
    }

    private static <B, T extends B> T cast(Class type, B value) {
      return Primitives.wrap(type).cast(value);
    }

    /**
     * Returns a new immutable class-to-instance map containing the entries
     * provided to this builder.
     *
     * @throws IllegalArgumentException if duplicate keys were added
     */
    public ImmutableClassToInstanceMap<B> build() {
      ImmutableMap<Class map = mapBuilder.build();
      if (map.isEmpty()) {
        return of();
      } else {
        return new ImmutableClassToInstanceMap<B>(map);
      }
    }
  }

  /**
   * Returns an immutable map containing the same entries as {@code map}. If
   * {@code map} somehow contains entries with duplicate keys (for example, if
   * it is a {@code SortedMap} whose comparator is not <i>consistent with
   * equals</i>), the results of this method are undefined.
   *
   * <p>Note: Despite what the method name suggests, if {@code map} is
   * an {@code ImmutableClassToInstanceMap}, no copy will actually be performed.
   *
   * @throws NullPointerException if any key or value in {@code map} is null
   * @throws ClassCastException if any value is not an instance of the type
   *     specified by its key
   */
  public static <B, S extends B> ImmutableClassToInstanceMap copyOf(
      Map<? extends Class map) {
    if (map instanceof ImmutableClassToInstanceMap) {
      @SuppressWarnings("unchecked") // covariant casts safe (unmodifiable)
      // Eclipse won't compile if we cast to the parameterized type.
      ImmutableClassToInstanceMap<B> cast = (ImmutableClassToInstanceMap) map;
      return cast;
    }
    return new Builder<B>().putAll(map).build();
  }

  private final ImmutableMap<Class delegate;

  private ImmutableClassToInstanceMap(ImmutableMap<Class delegate) {
    this.delegate = delegate;
  }

  @Override
  protected Map<Class delegate() {
    return delegate;
  }

  @Override
  @SuppressWarnings("unchecked") // value could not get in if not a T
  @Nullable
  public <T extends B> T getInstance(Class type) {
    return (T) delegate.get(checkNotNull(type));
  }

  /**
   * Guaranteed to throw an exception and leave the map unmodified.
   *
   * @throws UnsupportedOperationException always
   * @deprecated Unsupported operation.
   */
  @CanIgnoreReturnValue
  @Deprecated
  @Override
  public <T extends B> T putInstance(Class type, T value) {
    throw new UnsupportedOperationException();
  }

  Object readResolve() {
    return isEmpty() ? of() : this;
  }
}