001/*
002 * Copyright (c) 2016-2017 Chris K Wensel <chris@wensel.net>. All Rights Reserved.
003 * Copyright (c) 2007-2017 Xplenty, Inc. All Rights Reserved.
004 *
005 * Project and contact information: http://www.cascading.org/
006 *
007 * This file is part of the Cascading project.
008 *
009 * Licensed under the Apache License, Version 2.0 (the "License");
010 * you may not use this file except in compliance with the License.
011 * You may obtain a copy of the License at
012 *
013 *     http://www.apache.org/licenses/LICENSE-2.0
014 *
015 * Unless required by applicable law or agreed to in writing, software
016 * distributed under the License is distributed on an "AS IS" BASIS,
017 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
018 * See the License for the specific language governing permissions and
019 * limitations under the License.
020 */
021
022package cascading.util;
023
024import java.io.Serializable;
025import java.util.Comparator;
026
027/**
028 * Class NullNotEquivalentComparator simply returns -1 if the lhs is null, 1 if the rhs is null, or
029 * the result of {@code lhs.compareTo(rhs)}.
030 * <p>
031 * Use this {@link Comparator} when performing a {@link cascading.pipe.CoGroup} that needs SQL like semantics.
032 */
033public class NullNotEquivalentComparator implements Comparator<Comparable>, Serializable
034  {
035  @Override
036  public int compare( Comparable lhs, Comparable rhs )
037    {
038    if( lhs == null )
039      return -1;
040
041    if( rhs == null )
042      return 1;
043
044    return lhs.compareTo( rhs );
045    }
046  }