/*
    * Copyright (C) 2007 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.common.base.Objects;
  
  import java.util.Map.Entry;
  
  import javax.annotation.Nullable;
  
  /**
   * Implementation of the {@code equals}, {@code hashCode}, and {@code toString}
   * methods of {@code Entry}.
   *
   * @author Jared Levy
   */
  @GwtCompatible
  abstract class AbstractMapEntry<K, V> implements Entry<K, V> {
  
    @Override
    public abstract K getKey();
  
    @Override
    public abstract V getValue();
  
    @Override
    public V setValue(V value) {
      throw new UnsupportedOperationException();
    }
  
    @Override public boolean equals(@Nullable Object object) {
      if (object instanceof Entry) {
        Entry<?, ?> that = (Entry<?, ?>) object;
        return Objects.equal(this.getKey(), that.getKey())
            && Objects.equal(this.getValue(), that.getValue());
      }
      return false;
    }
  
    @Override public int hashCode() {
      K k = getKey();
      V v = getValue();
      return ((k == null) ? 0 : k.hashCode()) ^ ((v == null) ? 0 : v.hashCode());
    }
  
    /**
     * Returns a string representation of the form {@code {key}={value}}.
     */
    @Override public String toString() {
      return getKey() + "=" + getValue();
    }
  }