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.Comparator;
025
026/**
027 * Class NullNotEquivalentComparator simply returns -1 if the lhs is null, 1 if the rhs is null, or
028 * the result of {@code lhs.compareTo(rhs)}.
029 * <p/>
030 * Use this {@link Comparator} when performing a {@link cascading.pipe.CoGroup} that needs SQL like semantics.
031 */
032public class NullNotEquivalentComparator implements Comparator<Comparable>, Serializable
033  {
034  @Override
035  public int compare( Comparable lhs, Comparable rhs )
036    {
037    if( lhs == null )
038      return -1;
039
040    if( rhs == null )
041      return 1;
042
043    return lhs.compareTo( rhs );
044    }
045  }