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import java.io.IOException;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.lib.input.MultipleInputs;
import org.apache.hadoop.mapreduce.lib.input.TextInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
 
 public class ReduceJoin {
 public static class CustsMapper extends Mapper <Object, Text, Text, Text>
 {
 public void map(Object key, Text value, Context context)
 throws IOException, InterruptedException 
 {
 String record = value.toString();
 String[] parts = record.split(",");
 context.write(new Text(parts[0]), new Text("cust   " + parts[1]));
 }
 }
 
 public static class TxnsMapper extends Mapper <Object, Text, Text, Text>
 {
 public void map(Object key, Text value, Context context) 
 throws IOException, InterruptedException 
 {
 String record = value.toString();
 String[] parts = record.split(",");
 context.write(new Text(parts[2]), new Text("tnxn   " + parts[3]));
 }
 }
 
 public static class ReduceJoinReducer extends Reducer <Text, Text, Text, Text>
 {
 public void reduce(Text key, Iterable<Text> values, Context context)
 throws IOException, InterruptedException 
 {
 String name = "";
 double total = 0.0;
 int count = 0;
 for (Text t : values) 
 { 
 String parts[] = t.toString().split("  ");
 if (parts[0].equals("tnxn")) 
 {
 count++;
 total += Float.parseFloat(parts[1]);
 } 
 else if (parts[0].equals("cust")) 
 {
 name = parts[1];
 }
 }
 String str = String.format("%d %f", count, total);
 context.write(new Text(name), new Text(str));
 }
 }
 
 public static void main(String[] args) throws Exception {
 Configuration conf = new Configuration();
 Job job = new Job(conf, "Reduce-side join");
 job.setJarByClass(ReduceJoin.class);
 job.setReducerClass(ReduceJoinReducer.class);
 job.setOutputKeyClass(Text.class);
 job.setOutputValueClass(Text.class);
  
 MultipleInputs.addInputPath(job, new Path(args[0]),TextInputFormat.class, CustsMapper.class);
 MultipleInputs.addInputPath(job, new Path(args[1]),TextInputFormat.class, TxnsMapper.class);
 Path outputPath = new Path(args[2]);
  
 FileOutputFormat.setOutputPath(job, outputPath);
 outputPath.getFileSystem(conf).delete(outputPath);
 System.exit(job.waitForCompletion(true) ? 0 : 1);
 }
 }