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  }