SequenceElement.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.client.common.util;

/**
 * Wrapper for an element in a sequence
 * <p>
 * Implementations must enforce the contract that
 * element.getNext().getPrev() == element.getPrev().getNext() == element
 *
 * @author danilatos@google.com (Daniel Danilatos)
 * @param <T>
 */
public interface SequenceElement<T> {

  /**
   * @return Next element in the sequence (wraps)
   */
  SequenceElement<T> getNext();

  /**
   * @return Previous element in the sequence (wraps)
   */
  SequenceElement<T> getPrev();

  /**
   * @return Boxed value
   */
  T value();
}