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;
/**
* 題目:學生成績普通版
*
* 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、每一個course的最高分,最低分,平均分
返回結果格式:
course max=95 min=22 avg=55
例子:
computer max=99 min=48 avg=75
解題思路:在map以course作爲key值,其餘部分作爲value,在reduce中設置變量max,min,avg,通過累計求出,並設置格式
2、求該成績表當中出現了相同分數的分數,還有次數,以及該分數的人
返回結果的格式:
科目 分數 次數 該分數的人
例子:
computer 85 3 huangzitao,liujialing,huangxiaoming
解題思路:求某科目中出現系統分數的人數以及分數,map以科目和分數作爲key值,進行分組,在reduce中進行計數,當計數結果大於1時,輸出分數,人數和人名
*/
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(StudentScoresMapper.class);
// job.setReducerClass(StudentScoresReducer.class);
job.setMapperClass(StudentScoresMapper2.class);
job.setReducerClass(StudentScoresReducer2.class);
// job.setOutputKeyClass(Text.class);
// job.setOutputValueClass(IntWritable.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);
}
/**
* 第一題
*/
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);
}
}
/**
* 第一題
*/
public static class StudentScoresReducer extends Reducer<Text,IntWritable,Text,Text> {
private Text outValue = new Text();
@Override
protected void reduce(Text key, Iterable<IntWritable> values, Context context) throws IOException, InterruptedException {
int min = 1000 ;
int max = 0 ;
int avg ;
int sum = 0 ;
int count = 0 ;
//方法一:最大最小通過逐一比較得到
// for (IntWritable val:
// values) {
// int score = val.get();
// if(max < score){
// max = score;
// }
// if(min > score){
// min = score ;
// }
// sum += score ;
// count++ ;
// }
// avg = sum /count ;
// String outStr = "max="+max+" min="+min+" avg="+avg;
// outValue.set(outStr);
//方法二:最大最小值通過集合數組得到
List<Integer> 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);
}
}
/**
* 第二題
*/
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);
}
}
/**
* 第二題
*/
public static class StudentScoresReducer2 extends Reducer<Text,Text,Text,Text>{
private Text outValue = new Text();
@Override
protected void reduce(Text key, Iterable<Text> 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++;
}
//如果count大於等於2,說明有分數重合的
if(count >= 2 ){
outValue.set(count+" "+sb.toString());
context.write(key,outValue);
}
}
}
}
wordcount 學生成績普通版
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