输出english成绩，让你在考试中脱颖而出，Hadoop框架商店mappereduce利用

package ch3; import java.io.IOException; import org.apache.hadoop.conf.Configuration; import org.apache.hadoop.fs.Path; import org.apache.hadoop.io.LongWritable; import org.apache.hadoop.io.Text; import org.apache.hadoop.mapreduce.Job; import org.apache.hadoop.mapreduce.lib.input.FileInputFormat; import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat; public class EnglishMain { public static void main(String[] args) throws Exception { Configuration conf = new Configuration(); Job job = Job.getInstance(conf); job.setJarByClass(EnglishMain.class); job.setMapperClass(EnglishMapper.class); job.setReducerClass(EnglishReducer.class); job.setMapOutputKeyClass(LongWritable.class); job.setMapOutputValueClass(LongWritable.class); job.setOutputKeyClass(LongWritable.class); job.setOutputValueClass(LongWritable.class); FileInputFormat.setInputPaths(job, new Path(args[0])); FileOutputFormat.setOutputPath(job, new Path(args[1])); job.waitForCompletion(true); } } package ch3; import java.io.IOException; import org.apache.hadoop.io.IntWritable; import org.apache.hadoop.io.LongWritable; import org.apache.hadoop.io.Text; import org.apache.hadoop.mapreduce.Mapper; import org.apache.hadoop.mapreduce.Mapper.Context; public class EnglishMapper extends Mapper<LongWritable,Text, LongWritable, LongWritable> { @Override protected void map(LongWritable key1,Text value1, Context context) throws IOException, InterruptedException { String data = value1.toString(); String[] words = data.split(","); context.write(new LongWritable(Integer.parseInt(words[1])),new LongWritable(Integer.parseInt(words[5]))); } } package ch3; import java.io.IOException; import org.apache.hadoop.io.LongWritable; import org.apache.hadoop.io.Text; import org.apache.hadoop.mapreduce.Reducer; import org.apache.hadoop.mapreduce.Reducer.Context; public class EnglishReducer extends Reducer<LongWritable, LongWritable,LongWritable, LongWritable> { @Override protected void reduce(LongWritable k3, Iterable<LongWritable> v3,Context context) throws IOException,InterruptedException { long sum = 0; long count = 0; for(LongWritable v:v3) { sum+=v.get(); count+=1; } context.write(k3, new LongWritable(sum / count)); } }