我只是在学习Map缩小的工作。我做了一件事，我的作业，我必须改变我的代码接受另一个文本文件作为输入和输出必须显示与最大，最小，和平均金额年的位置。这是我输入的一行的示例： Calgary,AB,2009-01-07,604680,12694,2.5207754,0.065721168,0.025668362,0.972051954,0.037000279,0.022319018,,,0.003641149,,,0.002936745,,,0.016723641 输出应该是这样的： Calgary 2009 Average is: Max: Min: 这是我的代码，它给出了txt文件并计算平均值，最小值和最大值：

public class AverageMinMax {

public static class Map extends Mapper<LongWritable,Date,Text,Text> {

    //private static final FloatWritable rep= new  FloatWritable(1);
        public void map(LongWritable key,Text value,Context context)
        throws IOException, InterruptedException {
                context.write(new Text("Map_Output"), value);
        };
    }
      public static class Combiner extends Reducer<Text,Text,Text,Text>
      {
      public void reduce(Text key,Iterable<Text> values,Context context) throws IOException,InterruptedException
          {
             Integer NumberOfValues=0;
             double sum=0D;
             double min=0D;
             double max=0D;
             //double min=values.get(0);
              Iterator<Text> itr = values.iterator();
              //convertString=values(0);
              while(itr.hasNext())
              {
                  String TexttoString = itr.next().toString();
                  Double value = Double.parseDouble(TexttoString);
                  if(value<min)
                  {
                      min=value;
                  }
                  if(value>max)
                  {
                      max=value;
                  }
                  NumberOfValues++;
                  sum+=value;
              }
               Double average = sum/NumberOfValues;
                context.write(new Text("Combiner_output"), new Text(average + "," + NumberOfValues+","+min+","+max));
          };
      }
 public static class Reduce extends
       Reducer<Text,Text,Text,Text> {
      public void reduce(Text key, Iterable<Text> values,
        Context context) throws IOException, InterruptedException {
           Integer totalNumberOfValues= 0;
          Double sum=0.00;
          Double min=0D;
          Double max=0D;
          Iterator<Text> itr = values.iterator();
            while(itr.hasNext())
          {
              String TexttoString = itr.next().toString();
              String[] split_String = TexttoString.split(",");
              Double average = Double.parseDouble(split_String[0]);
              Integer NumberOfValues = Integer.parseInt(split_String[1]);
              Double minValue=Double.parseDouble(split_String[2]);
              Double maxValue=Double.parseDouble(split_String[3]);
              if(minValue<min)
              {
                  min=minValue;
              }
              if(maxValue>max)
              {
                  max=maxValue;
              }
              sum+=(average*NumberOfValues);
              totalNumberOfValues+=NumberOfValues;   
          } 
          Double average= sum/totalNumberOfValues;
          context.write(new Text("Average and Minimum and Max is"), new Text(average.toString()+" and "+ min.toString()+" and "+ max.toString()));
          };
     }
     public static void main(String[] args) throws Exception {

         Configuration conf = new Configuration();
         Job job=new Job(conf,"AverageMinMax.class");
         job.setJarByClass(AverageMinMax.class);
         job.setJobName("MapReduceAssignment");
         //JobConf conf = new JobConf(Hadoop_map_reduce.class);

        //conf.setJobName("Hadoop_assignment");
         // Configuration conf = new Configuration();
      //Job job = new Job(conf, "maxmin");
      //job.setJarByClass(Hadoop_map_reduce.class);
     // FileSystem fs = FileSystem.get(conf);
    /*  if (fs.exists(new Path(args[1]))) {
       fs.delete(new Path(args[1]), true);
      }*/
         job.setOutputKeyClass(Text.class);
         job.setOutputValueClass(Text.class);

         //job.setNumReduceTasks(1);

         job.setMapperClass(Map.class);

        job.setReducerClass(Reduce.class);
         job.setCombinerClass(Combiner.class);

        job.setInputFormatClass(TextInputFormat.class);
        job.setOutputFormatClass(TextOutputFormat.class);

     FileInputFormat.addInputPath(job, new Path(args[0]));
    //  FileOutputFormat.setOutputPath(job, new Path(args[1]));
        //FileInputFormat.addInputPath(job, new Path("/home/cloudera/Desktop/assign2"));
        FileOutputFormat.setOutputPath(job, new Path(args[1]));
      //  FileOutputFormat.setOutputPath(job, new Path(" user/cloudera/output"));
      job.waitForCompletion(true);
     }

}
所以，我的第一个问题是我不知道如何在Map器中转换日期，以及如何找到2个键并在输出中显示。我是说怎么重写这段代码！
我很感激你的帮助