package com.Practice.AverageScores;
import com.Practice.SameFriend.SameFriend;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
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 java.io.IOException;
import java.util.StringTokenizer;
/**
* 求學生平均成績
* 計算學生考試平均成績 源數據:
張三 98
李四 96
王五 95
張三 90
李四 92
王五 99
張三 80
李四 90
王五 94
張三 82
李四 92
*/
public class AverageScores {
public static void main(String[] args) throws IOException, ClassNotFoundException, InterruptedException {
Configuration conf = new Configuration();
FileSystem fs = FileSystem.get(conf);
Job job = Job.getInstance(conf);
job.setJar("wordcountJar/wordcount.jar");
job.setMapperClass(AverageScoresMapper.class);
job.setReducerClass(AverageScoresReducer.class);
job.setOutputKeyClass(Text.class);
job.setOutputValueClass(IntWritable.class);
Path inputPath = new Path("input/AverageScore");
Path outputPath = new Path("output/AverageScore");
if(fs.isDirectory(outputPath)){
fs.delete(outputPath,true);
}
FileInputFormat.setInputPaths(job,inputPath);
FileOutputFormat.setOutputPath(job,outputPath);
boolean waitForCompletion = job.waitForCompletion(true);
System.exit(waitForCompletion ? 0 : 1 );
}
public static class AverageScoresMapper extends Mapper<LongWritable,Text,Text,IntWritable> {
private Text outKey = new Text();
private IntWritable outValue = new IntWritable();
@Override
protected void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {
String[] splits = value.toString().split("\t");
outKey.set(splits[0]);
outValue.set(Integer.parseInt(splits[1]));
context.write(outKey,outValue);
}
}
public static class AverageScoresReducer extends Reducer<Text,IntWritable,Text,IntWritable> {
private IntWritable outValue = new IntWritable();
@Override
protected void reduce(Text key, Iterable<IntWritable> values, Context context) throws IOException, InterruptedException {
int avg = 0 ;
int sum = 0 ;
int count = 0 ;
for (IntWritable val :
values) {
int score = val.get();
sum += score ;
count ++ ;
}
avg = sum /count ;
outValue.set(avg);
context.write(key,outValue);
}
}
}
wordcount 求學生平均成績
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