Scala实现Mapreduce程序1-----求平均数

输入：

语文成绩：

a　　89

b　　88

c　　90

d　　77

数学成绩:

a　　80

b　　90

c　　98

d　　98

输出：

a　　84.5

b　　89

c　　94

d　　87.5

Scala程序实现：按照名字分组，然后计算总成绩以及课程个数

object AverageScore {
  def main(args: Array[String]): Unit = {
    val sc=new SparkContext(new SparkConf().setMaster("local"))
    val one=sc.textFile("/spark/test/",2)
    val line=one.filter(_.trim.length>0).map(text=>{
      (text.split("\t")(0).trim,text.split("\t")(1).trim.toInt)
    }).groupByKey().map(text=>{
      var sum=0;
      var num=0.0;
      for(x<-text._2){
        sum=sum+text._1.toInt;
        num+=1
      }
     val avg=sum/num
      val format=f"$avg%1.2f".toDouble
      (text._1,format)
    }).collect().foreach(x=>println("name"+x._1+"Average score"+x._2))
  }

}

用Mapreduce实现：

package HadoopvsSpark;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.DoubleWritable;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.LongWritable;
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;
import scala.tools.cmd.gen.AnyVals;

import java.io.IOException;

/**
 * Created by Administrator on 2017/5/25.
 */
public class AverageScore {
    public static class AverageMapper extends Mapper<LongWritable,Text,Text,IntWritable>{
        public void map(Text key,IntWritable value,Context context) throws IOException, InterruptedException {
            String line=key.toString();
            if(line.trim().length()>0){
                String[] arr=line.split( "\t" );
                context.write( new Text( arr[0] ),new IntWritable( Integer.valueOf( arr[1]) ) );
            }
        }
    }

    public static class AverageReducer extends Reducer<Text,IntWritable,Text,DoubleWritable>{
        public void reduce(Text key,Iterable<IntWritable> values,Context context) throws IOException, InterruptedException {
            int sum=0;
            for(IntWritable val:values){
                sum+=val.get();
            }
            context.write( key,new DoubleWritable( sum/3.0 ) );
        }
    }
    public static void main(String[] args) throws IOException, ClassNotFoundException, InterruptedException {
        Configuration conf=new Configuration();
        Job job=new Job();
        job.setJarByClass( AverageScore.class );

        job.setMapperClass( AverageMapper.class );
        job.setMapOutputKeyClass( Text.class );
        job.setMapOutputValueClass( IntWritable.class );

        job.setReducerClass( AverageReducer.class );
        job.setOutputKeyClass( Text.class );
        job.setOutputValueClass( DoubleWritable.class );

        FileInputFormat.addInputPath( job,new Path(args[0]) );
        Path outputdir=new Path( args[1] );
        FileSystem fs=FileSystem.get( conf );
        if(fs.exists( outputdir )){
            fs.delete( outputdir,true );
        }
        FileOutputFormat.setOutputPath(job,outputdir );
        System.out.println(job.waitForCompletion( true )?0:1);

    }
}

参考博客：
http://blog.csdn.net/kwu_ganymede/article/details/50482948