content: /*
   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements.  See the NOTICE file distributed with
   * this work for additional information regarding copyright ownership.
   * The ASF licenses this file to you 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 org.apache.calcite.linq4j;
  
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  import java.util.List;
  import java.util.Map;
  
  import static java.util.Objects.requireNonNull;
  
  /**
   * Implementation of {@link Grouping}.
   *
   * @param <K> Key type
   * @param <V> Value type
   */
  @SuppressWarnings("type.argument.type.incompatible")
  class GroupingImpl<K extends Object, V> extends AbstractEnumerable<V>
      implements Grouping<K, V>, Map.Entry<K, Enumerable<V>> {
    private final K key;
    private final List<V> values;
  
    GroupingImpl(K key, List<V> values) {
      this.key = requireNonNull(key, "key");
      this.values = requireNonNull(values, "values");
    }
  
    @Override public String toString() {
      return key + ": " + values;
    }
  
    /** {@inheritDoc}
     *
     * <p>Computes hash code consistent with
     * {@link java.util.Map.Entry#hashCode()}. */
    @Override public int hashCode() {
      return key.hashCode() ^ values.hashCode();
    }
  
    @Override public boolean equals(@Nullable Object obj) {
      return obj instanceof GroupingImpl
             && key.equals(((GroupingImpl) obj).key)
             && values.equals(((GroupingImpl) obj).values);
    }
  
    // implement Map.Entry
    @Override public Enumerable<V> getValue() {
      return Linq4j.asEnumerable(values);
    }
  
    // implement Map.Entry
    @Override public Enumerable<V> setValue(Enumerable<V> value) {
      // immutable
      throw new UnsupportedOperationException();
    }
  
    // implement Map.Entry
    // implement Grouping
    @Override public K getKey() {
      return key;
    }
  
    @Override public Enumerator<V> enumerator() {
      return Linq4j.enumerator(values);
    }
  }
  