编写MapReduce程序对手机流量数据进行分析得到总的上传流量、总的下载流量、总流量之和

假设手机流量数据的格式为：每行记录包含手机号、上传流量、下载流量，以逗号分隔。

Map阶段：

1. 将每行记录按照逗号分隔成三个字段，分别表示手机号、上传流量、下载流量。
2. 将手机号作为键，上传流量和下载流量作为值，发射到Reducer。

Reduce阶段：

1. 对于每个手机号，累加其上传流量和下载流量，得到总的上传流量和总的下载流量。
2. 将总的上传流量和总的下载流量相加，得到总流量之和。

示例代码：

Map阶段：

public class FlowCountMapper extends Mapper<LongWritable, Text, Text, IntWritable> {
    private Text phone = new Text();
    private IntWritable upload = new IntWritable();
    private IntWritable download = new IntWritable();

    @Override
    protected void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {
        String line = value.toString();
        String[] fields = line.split(",");
        if (fields.length == 3) {
            phone.set(fields[0]);
            upload.set(Integer.parseInt(fields[1]));
            download.set(Integer.parseInt(fields[2]));
            context.write(phone, upload);
            context.write(phone, download);
        }
    }
}

Reduce阶段：

public class FlowCountReducer extends Reducer<Text, IntWritable, Text, IntWritable> {
    private IntWritable totalUpload = new IntWritable();
    private IntWritable totalDownload = new IntWritable();

    @Override
    protected void reduce(Text key, Iterable<IntWritable> values, Context context) throws IOException, InterruptedException {
        int uploadSum = 0;
        int downloadSum = 0;
        for (IntWritable value : values) {
            if (value.get() > 0) {
                uploadSum += value.get();
            } else {
                downloadSum += value.get();
            }
        }
        totalUpload.set(uploadSum);
        totalDownload.set(downloadSum);
        context.write(key, totalUpload);
        context.write(key, totalDownload);
    }
}

Driver代码：

public class FlowCountDriver {
    public static void main(String[] args) throws Exception {
        Configuration conf = new Configuration();
        Job job = Job.getInstance(conf);

        job.setJarByClass(FlowCountDriver.class);

        job.setMapperClass(FlowCountMapper.class);
        job.setReducerClass(FlowCountReducer.class);

        job.setMapOutputKeyClass(Text.class);
        job.setMapOutputValueClass(IntWritable.class);
        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(IntWritable.class);

        FileInputFormat.setInputPaths(job, new Path(args[0]));
        FileOutputFormat.setOutputPath(job, new Path(args[1]));

        boolean result = job.waitForCompletion(true);
        System.exit(result ? 0 : 1);
    }
}
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