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 }