package com.Practice.StudentScores;
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.ArrayList;
import java.util.Collections;
import java.util.List;
/**
* 题目：学生成绩普通版
*
* computer,huangxiaoming,85
computer,xuzheng,54
computer,huangbo,86
computer,liutao,85
computer,huanglei,99
computer,liujialing,85
computer,liuyifei,75
computer,huangdatou,48
computer,huangjiaju,88
computer,huangzitao,85
english,zhaobenshan,57
english,liuyifei,85
english,liuyifei,76
english,huangdatou,48
english,zhouqi,85
english,huangbo,85
english,huangxiaoming,96
english,huanglei,85
english,liujialing,75
algorithm,liuyifei,75
algorithm,huanglei,76
algorithm,huangjiaju,85
algorithm,liutao,85
algorithm,huangdou,42
algorithm,huangzitao,81
math,wangbaoqiang,85
math,huanglei,76
math,huangjiaju,85
math,liutao,48
math,xuzheng,54
math,huangxiaoming,85
math,liujialing,85
*
* 1、每一个course的最高分，最低分，平均分
返回结果格式：
course max=95 min=22 avg=55
例子：
computer max=99 min=48 avg=75
解题思路：在map以course作为key值，其余部分作为value，在reduce中设置变量max，min，avg，通过累计求出，并设置格式
2、求该成绩表当中出现了相同分数的分数，还有次数，以及该分数的人
返回结果的格式：
科目 分数 次数 该分数的人
例子：
computer 85 3 huangzitao,liujialing,huangxiaoming
解题思路：求某科目中出现系统分数的人数以及分数，map以科目和分数作为key值，进行分组，在reduce中进行计数，当计数结果大于1时，输出分数，人数和人名
*/
public class StudentScores1 {
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(StudentScoresMapper2.class);
job.setReducerClass(StudentScoresReducer2.class);
job.setOutputKeyClass(Text.class);
job.setOutputValueClass(Text.class);
Path inputPath = new Path("input/studentScores");
Path outputPath = new Path("output/studentScores");
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);
}
/**
* 第一题
*/
public static class StudentScoresMapper extends Mapper<LongWritable,Text,Text,IntWritable> {
private IntWritable outValue = new IntWritable();
private Text outKey = new Text();
@Override
protected void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {
String[] splits = value.toString().split(",");
outKey.set(splits[0]);
outValue.set(Integer.parseInt(splits[2]));
context.write(outKey,outValue);
}
}
/**
* 第一题
*/
public static class StudentScoresReducer extends Reducer<Text,IntWritable,Text,Text> {
private Text outValue = new Text();
@Override
protected void reduce(Text key, Iterable values, Context context) throws IOException, InterruptedException {
int min = 1000 ;
int max = 0 ;
int avg ;
int sum = 0 ;
int count = 0 ;
List scores = new ArrayList<>();
for (IntWritable val :
values) {
scores.add(val.get());
sum += val.get();
count++;
}
Collections.sort(scores);
min = scores.get(0);
max = scores.get(scores.size()-1);
avg = sum / count ;
String outStr = "max="+max+" min="+min+" avg="+avg;
outValue.set(outStr);
context.write(key,outValue);
}
}
/**
* 第二题
*/
public static class StudentScoresMapper2 extends Mapper<LongWritable,Text,Text,Text>{
private Text outKey = new Text();
private Text outValue = new Text();
@Override
protected void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {
String[] splits = value.toString().split(",");
outKey.set(splits[0]+"\t"+splits[2]);
outValue.set(splits[1]);
context.write(outKey,outValue);
}
}
/**
* 第二题
*/
public static class StudentScoresReducer2 extends Reducer<Text,Text,Text,Text>{
private Text outValue = new Text();
@Override
protected void reduce(Text key, Iterable values, Context context) throws IOException, InterruptedException {
StringBuilder sb = new StringBuilder();
int count = 0 ;
for (Text text :
values) {
if(sb.length()!=0){
sb.append(",");
}
sb.append(text);
count++;
}
if(count >= 2 ){
outValue.set(count+" "+sb.toString());
context.write(key,outValue);
}
}
}
}
