MapReduceを使用して、num.txtの2で始まる番号を削除し、結果をnum2.txtとして保存します
package MR_9_12;
import java.io.IOException;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
public class shuziMR {
//使用MR的处理方式,去除num.txt中以2开头的数字,将结果保存为num2.txt
public static class MyMapper extends Mapper<LongWritable, Text, Text , NullWritable> {
@Override
protected void map(LongWritable key, Text value, Mapper<LongWritable, Text, Text, NullWritable>.Context context)
throws IOException, InterruptedException {
String line = value.toString();
String[] words = line.split(",");
for (String word : words) {
if(!word.startsWith("2"))
context.write(new Text(word), NullWritable.get());
}
}
}
public static class MyReducer extends Reducer<Text, NullWritable, Text, NullWritable> {
@Override
protected void reduce(Text arg0, Iterable<NullWritable> arg1,
Reducer<Text, NullWritable, Text, NullWritable>.Context arg2) throws IOException, InterruptedException {
// TODO Auto-generated method stub
// super.reduce(arg0, arg1, arg2);
for (NullWritable nullWritable : arg1) {
arg2.write(arg0, nullWritable);
}
}
}
public static void main(String[] args) throws Exception {
Configuration conf = new Configuration();
Job job = Job.getInstance(conf);
job.setJarByClass(shuziMR.class);
job.setMapperClass(MyMapper.class);
job.setReducerClass(MyReducer.class);
job.setMapOutputKeyClass(Text.class);
job.setMapOutputValueClass(NullWritable.class);
job.setOutputKeyClass(Text.class);
job.setOutputValueClass(NullWritable.class);
FileInputFormat.setInputPaths(job, new Path("src/data/1.txt"));
FileOutputFormat.setOutputPath(job, new Path("out/1ed.txt"));
job.waitForCompletion(true);
}
}