| /** |
| * 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 class implements a value aggregator that maintain the biggest of |
| * a sequence of strings. |
| * |
| */ |
| @InterfaceAudience.Public |
| @InterfaceStability.Stable |
| public class StringValueMax implements ValueAggregator<String> { |
| |
| String maxVal = null; |
| |
| /** |
| * the default constructor |
| * |
| */ |
| public StringValueMax() { |
| reset(); |
| } |
| |
| /** |
| * add a value to the aggregator |
| * |
| * @param val |
| * a string. |
| * |
| */ |
| public void addNextValue(Object val) { |
| String newVal = val.toString(); |
| if (this.maxVal == null || this.maxVal.compareTo(newVal) < 0) { |
| this.maxVal = newVal; |
| } |
| } |
| |
| |
| /** |
| * @return the aggregated value |
| */ |
| public String getVal() { |
| return this.maxVal; |
| } |
| |
| /** |
| * @return the string representation of the aggregated value |
| */ |
| public String getReport() { |
| return maxVal; |
| } |
| |
| /** |
| * reset the aggregator |
| */ |
| public void reset() { |
| maxVal = null; |
| } |
| |
| /** |
| * @return return an array of one element. The element is a string |
| * representation of the aggregated value. The return value is |
| * expected to be used by the a combiner. |
| */ |
| public ArrayList<String> getCombinerOutput() { |
| ArrayList<String> retv = new ArrayList<String>(1); |
| retv.add(maxVal); |
| return retv; |
| } |
| } |