    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  }