library/src/main/java/com/datatorrent/lib/util/ReversibleComparator.java

/*
 * Copyright (c) 2013 DataTorrent, Inc. ALL Rights Reserved.
 *
 * 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.datatorrent.lib.util;

import java.util.Comparator;

/**
 *
 * A comparator for ascending and descending lists<p>
 * <br>
 *
 * @since 0.3.2
 */
public class ReversibleComparator<E> implements Comparator<E>
{
  /**
   * Added default constructor for deserializer
   */
  public ReversibleComparator()
  {
  }

  /**
   *
   * @param flag true for ascending, false for descending
   */
  public ReversibleComparator(boolean flag)
  {
    ascending = flag;
  }
  public boolean ascending = true;

  /**
   * Compare function
   * @param e1
   * @param e2
   * @return e1.compareTo(e2) if acscending, else 0 - e1.compareTo(e2)
   */
  @SuppressWarnings("unchecked")
  @Override
  public int compare(E e1, E e2)
  {
    Comparable<? super E> ce1 = (Comparable<? super E>)e1;
    int ret = ce1.compareTo(e2);
    if (!ascending) {
      ret = 0 - ret;
    }
    return ret;
  }
}