    001    /*
    002     * Copyright (c) 2007-2014 Concurrent, 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
    021    package cascading.util;
    022
    023    import java.io.Serializable;
    024    import 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     */
    032    public 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      }