使用MapReduce和Hadoop的销售数据排序系统的代码，按月份升序和销售量降序排序

以下是使用MapReduce和Hadoop的销售数据排序系统的代码，按月份升序和销售量降序排序：

Mapper类：SalesMapper.java

import java.io.IOException;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Mapper;

public class SalesMapper extends Mapper<LongWritable, Text, Text, Text> {

    private Text outputKey = new Text();
    private Text outputValue = new Text();

    public void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {

        String[] record = value.toString().split(",");
        String month = record[0];
        String sales = record[1];

        outputKey.set(month);
        outputValue.set(sales);

        context.write(outputKey, outputValue);
    }
}

Reducer类：SalesReducer.java

import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Reducer;

public class SalesReducer extends Reducer<Text, Text, Text, Text> {

    private Text outputValue = new Text();

    public void reduce(Text key, Iterable<Text> values, Context context) throws IOException, InterruptedException {

        List<Integer> salesList = new ArrayList<Integer>();
        
        for (Text value : values) {
            salesList.add(Integer.parseInt(value.toString()));
        }

        // 对销售量进行降序排序
        Collections.sort(salesList, Collections.reverseOrder());

        StringBuilder sb = new StringBuilder();
        for (int sales : salesList) {
            sb.append(sales).append(",");
        }

        // 去掉最后一个逗号
        sb.setLength(sb.length() - 1);

        outputValue.set(sb.toString());

        context.write(key, outputValue);
    }
}

Driver类：SalesSortDriver.java

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.lib.input.TextInputFormat;
import org.apache.hadoop.mapreduce.lib.output.TextOutputFormat;

public class SalesSortDriver {

    public static void main(String[] args) throws Exception {

        Configuration conf = new Configuration();
        Job job = Job.getInstance(conf, "Sales Sort");

        job.setJarByClass(SalesSortDriver.class);

        job.setMapperClass(SalesMapper.class);
        job.setReducerClass(SalesReducer.class);

        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(Text.class);

        job.setInputFormatClass(TextInputFormat.class);
        job.setOutputFormatClass(TextOutputFormat.class);

        TextInputFormat.setInputPaths(job, new Path(args[0]));
        TextOutputFormat.setOutputPath(job, new Path(args[1]));

        job.waitForCompletion(true);
    }
}

在运行Hadoop作业时，您需要将输入数据以逗号分隔的格式存储在文本文件中，并将其传递给作业的第一个参数。作业的第二个参数将是输出目录。您可以在输出目录中找到按月份升序和销售量降序排序的结果。