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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.FloatWritable;
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.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
public class AverageGPA {
public static class TokenizerMapper
extends Mapper<Object, Text, Text, FloatWritable>{
public void map(Object key, Text value, Context context
) throws IOException, InterruptedException {
String[] record = value.toString().split(",");
String ID = record[0];
try {
Float gpa = Float.parseFloat(record[2]);
context.write(new Text(ID), new FloatWritable(gpa));
} catch (Exception e) {
e.printStackTrace();
}
}
}
public static class AverageReducer
extends Reducer<Text, FloatWritable, Text, Text> {
public void reduce(Text key, Iterable<FloatWritable> values,
Context context
) throws IOException, InterruptedException {
Float total = (float) 0;
int count = 0;
try {
for (FloatWritable var : values) {
total += var.get();
System.out.println("reducer " + var.get());
count++;
}
Float avg = (Float) total / count;
context.write(key, new Text(String.valueOf(avg)));
} catch (Exception e) {
e.printStackTrace();
}
}
}
public static void main(String[] args) throws Exception {
Configuration conf = new Configuration();
Job job = Job.getInstance(conf, "Average GPA");
job.setJarByClass(AverageGPA.class);
job.setMapperClass(TokenizerMapper.class);
//job.setCombinerClass(AverageReducer.class);
job.setReducerClass(AverageReducer.class);
// Map output key, value types
job.setOutputKeyClass(Text.class);
job.setOutputValueClass(FloatWritable.class);
FileInputFormat.addInputPath(job, new Path(args[0]));
FileOutputFormat.setOutputPath(job, new Path(args[1]));
System.exit(job.waitForCompletion(true) ? 0 : 1);
}
}
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