text: /*
   * Copyright (C) 2012 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.checkArgument;
  
  import com.google.common.annotations.GwtCompatible;
  import com.google.common.collect.ImmutableMap.IteratorBasedImmutableMap;
  import java.io.Serializable;
  import java.util.EnumMap;
  import org.checkerframework.checker.nullness.compatqual.NullableDecl;
  
  /**
   * Implementation of {@link ImmutableMap} backed by a non-empty {@link java.util.EnumMap}.
   *
   * @author Louis Wasserman
   */
  @GwtCompatible(serializable = true, emulated = true)
  @SuppressWarnings("serial") // we're overriding default serialization
  final class ImmutableEnumMap<K extends Enum<K>, V> extends IteratorBasedImmutableMap<K, V> {
    static <K extends Enum<K>, V> ImmutableMap<K, V> asImmutable(EnumMap<K, V> map) {
      switch (map.size()) {
        case 0:
          return ImmutableMap.of();
        case 1:
          Entry<K, V> entry = Iterables.getOnlyElement(map.entrySet());
          return ImmutableMap.of(entry.getKey(), entry.getValue());
        default:
          return new ImmutableEnumMap<>(map);
      }
    }
  
    private final transient EnumMap<K, V> delegate;
  
    private ImmutableEnumMap(EnumMap<K, V> delegate) {
      this.delegate = delegate;
      checkArgument(!delegate.isEmpty());
    }
  
    @Override
    UnmodifiableIterator<K> keyIterator() {
      return Iterators.unmodifiableIterator(delegate.keySet().iterator());
    }
  
    @Override
    public int size() {
      return delegate.size();
    }
  
    @Override
    public boolean containsKey(@NullableDecl Object key) {
      return delegate.containsKey(key);
    }
  
    @Override
    public V get(Object key) {
      return delegate.get(key);
    }
  
    @Override
    public boolean equals(Object object) {
      if (object == this) {
        return true;
      }
      if (object instanceof ImmutableEnumMap) {
        object = ((ImmutableEnumMap<?, ?>) object).delegate;
      }
      return delegate.equals(object);
    }
  
    @Override
    UnmodifiableIterator<Entry<K, V>> entryIterator() {
      return Maps.unmodifiableEntryIterator(delegate.entrySet().iterator());
    }
  
    @Override
    boolean isPartialView() {
      return false;
    }
  
    // All callers of the constructor are restricted to <K extends Enum<K>>.
    @Override
    Object writeReplace() {
      return new EnumSerializedForm<>(delegate);
    }
  
    /*
     * This class is used to serialize ImmutableEnumMap instances.
     */
    private static class EnumSerializedForm<K extends Enum<K>, V> implements Serializable {
      final EnumMap<K, V> delegate;
  
      EnumSerializedForm(EnumMap<K, V> delegate) {
        this.delegate = delegate;
      }
  
      Object readResolve() {
        return new ImmutableEnumMap<>(delegate);
      }
  
      private static final long serialVersionUID = 0;
    }
  }
  