    001/*
    002 * Copyright (c) 2007-2017 Xplenty, Inc. All Rights Reserved.
    003 *
    004 * Project and contact information: http://www.cascading.org/
    005 *
    006 * This file is part of the Cascading project.
    007 *
    008 * Licensed under the Apache License, Version 2.0 (the "License");
    009 * you may not use this file except in compliance with the License.
    010 * You may obtain a copy of the License at
    011 *
    012 *     http://www.apache.org/licenses/LICENSE-2.0
    013 *
    014 * Unless required by applicable law or agreed to in writing, software
    015 * distributed under the License is distributed on an "AS IS" BASIS,
    016 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    017 * See the License for the specific language governing permissions and
    018 * limitations under the License.
    019 */
    020
    021package cascading.util;
    022
    023import java.io.Serializable;
    024import java.util.Collections;
    025import java.util.Comparator;
    026
    027/**
    028 *
    029 */
    030public class NullSafeReverseComparator implements Comparator<Comparable<Object>>, Serializable
    031  {
    032  public static <T> Comparator<T> reverseOrder( Comparator<T> comparator )
    033    {
    034    if( comparator == null )
    035      return (Comparator<T>) new NullSafeReverseComparator();
    036
    037    return Collections.reverseOrder( comparator );
    038    }
    039
    040  @Override
    041  public int compare( Comparable<Object> lhs, Comparable<Object> rhs )
    042    {
    043    if( lhs == null && rhs == null )
    044      return 0;
    045
    046    if( lhs == null )
    047      return 1;
    048
    049    if( rhs == null )
    050      return -1;
    051
    052    return rhs.compareTo( lhs );
    053    }
    054  }