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.tuple; 023 024/** 025 * The Hasher allows a {@link java.util.Comparator} implementation to also be delegated to during hashCode generation 026 * during grouping partitioning. 027 * <p> 028 * If a Comparator is used to compare two types during grouping, its likely the {@code hashCode} value between 029 * the two objects will not be consistent. This allows to objects being equal to hash to the same bucket (reducer) 030 * during partitioning. 031 * <p> 032 * As of Cascading 3.0 null values will be passed to implementations of the Hasher interface. 033 */ 034public interface Hasher<V> 035 { 036 /** 037 * Return the hashCode of the given value. 038 * 039 * @param value may be null 040 * @return int hashCode of given value 041 */ 042 int hashCode( V value ); 043 }