    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.tuple;
    022
    023import java.util.Comparator;
    024
    025/**
    026 * The Comparison interface allows specific underlying type mechanisms to additionally return relevant
    027 * {@link Comparator} implementations when required internally.
    028 * <p/>
    029 * In the case of Hadoop, {@link org.apache.hadoop.io.serializer.Serialization} implementations that present
    030 * alternative serialization implementations for custom types manged by {@link Tuple}s should also
    031 * implement the {@link #getComparator(Class)} method.
    032 * <p/>
    033 * During runtime Cascading can identify and use the correct Comparator during grouping operations if it was
    034 * not given explicitly on the {@link Fields#setComparator(Comparable, java.util.Comparator)} family of methods.
    035 * <p/>
    036 * See the class {@link cascading.tuple.hadoop.BytesSerialization} for an example.
    037 * <p/>
    038 * see cascading.tuple.hadoop.BytesSerialization
    039 */
    040public interface Comparison<T>
    041  {
    042  Comparator<T> getComparator( Class<T> type );
    043  }