src/main/java/net/hydromatic/linq4j/GroupingImpl.java

/*
// Licensed to Julian Hyde under one or more contributor license
// agreements. See the NOTICE file distributed with this work for
// additional information regarding copyright ownership.
//
// Julian Hyde 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 net.hydromatic.linq4j;

import java.util.Collection;
import java.util.Map;

/**
 * Implementation of {@link Grouping}.
 *
 * @param <K> Key type
 * @param <V> Value type
 */
class GroupingImpl<K, V> extends AbstractEnumerable<V>
    implements Grouping<K, V>, Map.Entry<K, Enumerable<V>> {
  private final K key;
  private final Collection<V> values;

  GroupingImpl(K key, Collection<V> values) {
    this.key = key;
    this.values = values;
  }

  @Override
  public String toString() {
    return key + ": " + values;
  }

  @Override
  public int hashCode() {
    return (11 + key.hashCode()) * 37 + values.hashCode();
  }

  @Override
  public boolean equals(Object obj) {
    return obj instanceof GroupingImpl
           && key.equals(((GroupingImpl) obj).key)
           && values.equals(((GroupingImpl) obj).values);
  }

  // implement Map.Entry
  public Enumerable<V> getValue() {
    return Linq4j.asEnumerable(values);
  }

  // implement Map.Entry
  public Enumerable<V> setValue(Enumerable<V> value) {
    // immutable
    throw new UnsupportedOperationException();
  }

  // implement Map.Entry
  // implement Grouping
  public K getKey() {
    return key;
  }

  public Enumerator<V> enumerator() {
    return Linq4j.enumerator(values);
  }
}

// End GroupingImpl.java