Java example source code file (WellBehavedMap.java)

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Java - Java tags/keywords

abstractmapentry, entryset, forwardingmap, gwtcompatible, iterator, override, set, transformediterator, util, weakouter, wellbehavedmap

The WellBehavedMap.java Java example source code

/*
 * Copyright (C) 2011 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 com.google.common.annotations.GwtCompatible;
import com.google.j2objc.annotations.WeakOuter;

import java.util.Iterator;
import java.util.Map;
import java.util.Set;

/**
 * Workaround for
 * <a href="http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6312706">
 * EnumMap bug</a>. If you want to pass an {@code EnumMap}, with the
 * intention of using its {@code entrySet()} method, you should
 * wrap the {@code EnumMap} in this class instead.
 *
 * <p>This class is not thread-safe even if the underlying map is.
 *
 * @author Dimitris Andreou
 */
@GwtCompatible
final class WellBehavedMap<K, V> extends ForwardingMap {
  private final Map<K, V> delegate;
  private Set<Entry entrySet;

  private WellBehavedMap(Map<K, V> delegate) {
    this.delegate = delegate;
  }

  /**
   * Wraps the given map into a {@code WellBehavedEntriesMap}, which
   * intercepts its {@code entrySet()} method by taking the
   * {@code Set<K> keySet()} and transforming it to
   * {@code Set<Entry}. All other invocations are delegated as-is.
   */
  static <K, V> WellBehavedMap wrap(Map delegate) {
    return new WellBehavedMap<K, V>(delegate);
  }

  @Override
  protected Map<K, V> delegate() {
    return delegate;
  }

  @Override
  public Set<Entry entrySet() {
    Set<Entry es = entrySet;
    if (es != null) {
      return es;
    }
    return entrySet = new EntrySet();
  }

  @WeakOuter
  private final class EntrySet extends Maps.EntrySet<K, V> {
    @Override
    Map<K, V> map() {
      return WellBehavedMap.this;
    }

    @Override
    public Iterator<Entry iterator() {
      return new TransformedIterator<K, Entry(keySet().iterator()) {
        @Override
        Entry<K, V> transform(final K key) {
          return new AbstractMapEntry<K, V>() {
            @Override
            public K getKey() {
              return key;
            }

            @Override
            public V getValue() {
              return get(key);
            }

            @Override
            public V setValue(V value) {
              return put(key, value);
            }
          };
        }
      };
    }
  }
}