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.tuple; 022 023 /** 024 * The Hasher allows a {@link java.util.Comparator} implementation to also be delegated to during hashCode generation 025 * during grouping partitioning. 026 * <p/> 027 * If a Comparator is used to compare two types during grouping, its likely the {@code hashCode} value between 028 * the two objects will not be consistent. This allows to objects being equal to hash to the same bucket (reducer) 029 * during partitioning. 030 */ 031 public interface Hasher<V> 032 { 033 /** 034 * Return the hashCode of the given value. 035 * 036 * @param value will never be null 037 * @return int hashCode of given value 038 */ 039 int hashCode( V value ); 040 }