2018年安徽省大数据比赛MapReduce题目解答第二题

布满荆棘的人生 2023-08-17 17:48 84阅读 0赞

num.txt在此博客中：[https://blog.csdn.net/qq\_41479464/article/details/101922339][https_blog.csdn.net_qq_41479464_article_details_101922339]

使用MR的处理方式,去除num.txt中以2开头的数字,并且统计每个数字出现的次数将结果保存为num2.txt（10分）

** 主函数：**

import java.io.IOException;
    
    import org.apache.hadoop.conf.Configuration;
    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.lib.input.FileInputFormat;
    import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
    
    
    
    public class MapReduceNum {
    	public static void main(String[] args) throws IOException, ClassNotFoundException, InterruptedException {
    		Configuration conf = new Configuration();
    		Job job = Job.getInstance(conf,MapReduceNum.class.getSimpleName());
    		job.setJarByClass(MapReduceNum.class);
    		FileInputFormat.addInputPath(job, new Path(args[0]));
    		job.setMapperClass(MyMap.class);
    		job.setMapOutputKeyClass(Text.class);
    		job.setMapOutputValueClass(IntWritable.class);
    		
    		job.setReducerClass(MyRed.class);
    		job.setOutputKeyClass(Text.class);
    		job.setOutputValueClass(LongWritable.class);
    		FileOutputFormat.setOutputPath(job, new Path(args[1]));
    		job.waitForCompletion(true);
    		
    	}
    	
    
    }

Map函数：

import java.io.IOException;
    
    import org.apache.hadoop.io.IntWritable;
    import org.apache.hadoop.io.LongWritable;
    import org.apache.hadoop.io.Text;
    import org.apache.hadoop.mapreduce.Mapper;
    
    public class MyMap extends Mapper<LongWritable, Text, Text, IntWritable>{
    	@Override
    	protected void map(LongWritable key, Text value, Mapper<LongWritable, Text, Text, IntWritable>.Context context)
    			throws IOException, InterruptedException {
    		String line[] = value.toString().split(",");
    		for (String string : line) {
    			if(!string.startsWith("2"));
    			context.write(new Text(string),new IntWritable(1));
    		}		
    		
    	}
    
    }

Reduce函数：

import java.io.IOException;
    
    import org.apache.hadoop.io.IntWritable;
    import org.apache.hadoop.io.LongWritable;
    import org.apache.hadoop.io.Text;
    import org.apache.hadoop.mapreduce.Reducer;
    
    public class MyRed extends Reducer<Text, IntWritable, Text, LongWritable> {
    	@Override
    	protected void reduce(Text key, Iterable<IntWritable> values,
    			Reducer<Text, IntWritable, Text, LongWritable>.Context context) throws IOException, InterruptedException {
    		long count = 0l;
    		for (IntWritable val : values) {
    			count = count +val.get();
    		}
    		//将结果输出，输出到hdfs上
    		context.write(new Text(key), new LongWritable(count));
    	}
    
    }

[https_blog.csdn.net_qq_41479464_article_details_101922339]: https://blog.csdn.net/qq_41479464/article/details/101922339