org.apache.hadoop.mapreduce.lib.aggregate.ValueAggregator Maven / Gradle / Ivy
/**
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.hadoop.mapreduce.lib.aggregate;
import java.util.ArrayList;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
/**
* This interface defines the minimal protocol for value aggregators.
*
*/
@InterfaceAudience.Public
@InterfaceStability.Stable
public interface ValueAggregator {
/**
* add a value to the aggregator
*
* @param val the value to be added
*/
public void addNextValue(Object val);
/**
* reset the aggregator
*
*/
public void reset();
/**
* @return the string representation of the agregator
*/
public String getReport();
/**
*
* @return an array of values as the outputs of the combiner.
*/
public ArrayList getCombinerOutput();
}