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 }