ChainedHashSet.java

/**
 * 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.waveprotocol.wave.model.util;

import java.util.Set;

/**
 * @author danilatos@google.com (Daniel Danilatos)
 */
public class ChainedHashSet<T> extends ChainedData<Set<T>, Set<T>> {

  public static final ChainedHashSet<Object> EMPTY_ROOT = new ChainedHashSet<Object>();

  @SuppressWarnings("unchecked")
  public static <T> ChainedHashSet<T> emptyRoot() {
    return (ChainedHashSet<T>) EMPTY_ROOT;
  }

  /**
   * Root
   */
  public ChainedHashSet() {
    super(CollectionUtils.<T>hashSetDomain());
  }

  /**
   * Chained
   */
  public ChainedHashSet(ChainedHashSet<T> parent) {
    super(parent);
  }

  /** Create a child set */
  public ChainedHashSet<T> createExtension() {
    return new ChainedHashSet<T>(this);
  }
}