001    /**
002     * Licensed to the Apache Software Foundation (ASF) under one
003     * or more contributor license agreements.  See the NOTICE file
004     * distributed with this work for additional information
005     * regarding copyright ownership.  The ASF licenses this file
006     * to you under the Apache License, Version 2.0 (the
007     * "License"); you may not use this file except in compliance
008     * with the License.  You may obtain a copy of the License at
009     *
010     *     http://www.apache.org/licenses/LICENSE-2.0
011     *
012     * Unless required by applicable law or agreed to in writing, software
013     * distributed under the License is distributed on an "AS IS" BASIS,
014     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015     * See the License for the specific language governing permissions and
016     * limitations under the License.
017     */
018    
019    package org.apache.hadoop.mapreduce.lib.aggregate;
020    
021    import java.util.ArrayList;
022    
023    import org.apache.hadoop.classification.InterfaceAudience;
024    import org.apache.hadoop.classification.InterfaceStability;
025    
026    /**
027     * This class implements a value aggregator that sums up 
028     * a sequence of long values.
029     * 
030     */
031    @InterfaceAudience.Public
032    @InterfaceStability.Stable
033    public class LongValueSum implements ValueAggregator<String> {
034    
035      long sum = 0;
036        
037      /**
038       *  the default constructor
039       *
040       */
041      public LongValueSum() {
042        reset();
043      }
044    
045      /**
046       * add a value to the aggregator
047       * 
048       * @param val
049       *          an object whose string representation represents a long value.
050       * 
051       */
052      public void addNextValue(Object val) {
053        this.sum += Long.parseLong(val.toString());
054      }
055        
056      /**
057       * add a value to the aggregator
058       * 
059       * @param val
060       *          a long value.
061       * 
062       */
063      public void addNextValue(long val) {
064        this.sum += val;
065      }
066        
067      /**
068       * @return the aggregated value
069       */
070      public long getSum() {
071        return this.sum;
072      }
073        
074      /**
075       * @return the string representation of the aggregated value
076       */
077      public String getReport() {
078        return ""+sum;
079      }
080    
081      /**
082       * reset the aggregator
083       */
084      public void reset() {
085        sum = 0;
086      }
087    
088      /**
089       * @return return an array of one element. The element is a string
090       *         representation of the aggregated value. The return value is
091       *         expected to be used by the a combiner.
092       */
093      public ArrayList<String> getCombinerOutput() {
094        ArrayList<String> retv = new ArrayList<String>(1);
095        retv.add(""+sum);
096        return retv;
097      }
098    }
099    
100