交通运输mapreduce做最大值最小值。

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最新推荐文章于 2024-07-01 02:25:02 发布

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分类专栏： mapreduce java学习文章标签：比赛

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本文介绍了如何运用Apache Hadoop的MapReduce框架解决交通运输数据中求最大值和最小值的问题。博客提供了具体的map、reduce代码实现，并在主类中配置和执行MapReduce任务。通过对输入数据进行处理，最终找到交通数据的极值。

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map代码：

package com.traffic;

import java.io.IOException;

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

public class MyTrafficMapper extends Mapper<LongWritable,Text,Text,Text> {
    String[] title=new String[44];
    @Override
    protected void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {
        String[] line=value.toString().split(",");
        //字节偏移量
        if(key.toString().equals("0")){
            title=line;
        }else {
            try {
                if (line.length > 43) {
                    for (int i = 0; i < 44; i++) {
                        context.write(new Text(title[i]), new Text(line[i]));
                    }
                }
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }
}

reduce代码：

package com.traffic;
import java.io.IOException;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Reducer;
public class MyTrafficReduce extends Reducer<Text,Text,Text,Text> {
    @Override
    protected void reduce(Text key, Iterable<Text> values, Context context) throws IOException, InterruptedException {
        //统计每列的最大值最小值
            float min = Float.MAX_VALUE;
            float max = Float.MIN_VALUE;
            int count=0;
            Pattern pattern=Pattern.compile("[0-9]+\\.?[0-9]+");
            for (Text value : values) {
                if (value.toString().equals("")){
                count+=1;
            }
                Matcher isNum=pattern.matcher(value.toString());
                if (isNum.matches()) {
                    float data = Float.parseFloat(value.toString());
                    if (data > max) {
                        max = data;
                    }
                    if (data < min) {
                        min = data;
                    }
                }
            }
            if (min!= Float.MAX_VALUE) {
                context.write(key, new Text(count+"\t"+min + "\t" + max));
            }else {
                context.write(key, new Text(count+"\t"+"无\t无"));
            }
    }
}

主类：
package com.traffic;

import java.io.IOException;

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.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;

public class MyTrafficDrive {
public static void main(String[] args) throws IOException, ClassNotFoundException, InterruptedException {
Configuration conf=new Configuration();
Job job= Job.getInstance();
job.setJarByClass(MyTrafficDrive.class);
job.setMapperClass(MyTrafficMapper.class);
job.setReducerClass(MyTrafficReduce.class);
SetJobs(job);
Path path=SetPath(job);
path.getFileSystem(conf).delete(path,true);
System.exit(job.waitForCompletion(true)?0:1);
}

private static Path SetPath(Job job) throws IOException {
    FileInputFormat.addInputPath(job,new Path("E:\\data1"));
    Path path=new Path("E:\\data1\\out");
    FileOutputFormat.setOutputPath(job,path);
    return path;
}
private static void SetJobs(Job job) {
    job.setMapOutputKeyClass(Text.class);
    job.setMapOutputValueClass(Text.class);
    job.setOutputKeyClass(Text.class);
    job.setOutputValueClass(Text.class);
}

}