MapReduce实验——计算整数的最大值最小值

最大值最小值"/>

MapReduce实验——计算整数的最大值最小值

计算整数的最大值最小值

Map类

package MaxMin_03;import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Mapper;import java.io.IOException;public class MyMap extendsMapper<LongWritable,Text, Text,LongWritable> {//为map设置一个固定的输出键private final Text keyText = new Text("K");private LongWritable val = new LongWritable(0);@Overrideprotected void map(LongWritable key,Text value,Context context) throws IOException, InterruptedException {//为val对象设置读取的数值val.set(Long.parseLong(value.toString()));context.write(keyText,val);}
}

Reduce类

package MaxMin_03;import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Reducer;import java.io.IOException;public class MyReduce extends Reducer<Text, LongWritable,Text,Text> {//设置变量max和min的初始值private long max = Long.MIN_VALUE;private long min = Long.MAX_VALUE;@Overrideprotected void reduce(Text key,Iterable<LongWritable> valueIn,Context context) throws IOException, InterruptedException {//循环得出最大值和最小值for(LongWritable val : valueIn){long tmp = val.get();if(tmp > max){max = tmp;}if(tmp < min){min = tmp;}}//最大值和最小值分别输出context.write(new Text("Max"),new Text(max + ""));context.write(new Text("Min"),new Text(min + ""));}
}

Job类

package MaxMin_03;import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;import org.apache.hadoop.io.Text;
import java.io.IOException;public class TestJob {public static void main(String[] args) throws IOException, ClassNotFoundException, InterruptedException {Configuration conf = new Configuration();//1、获取作业对象Job job = Job.getInstance(conf);//2、设置主类job.setJarByClass(TestJob.class);//3、设置job参数job.setMapperClass(MyMap.class);job.setReducerClass(MyReduce.class);//4 set map reduce output typejob.setMapOutputKeyClass(Text.class);job.setMapOutputValueClass(LongWritable.class);job.setOutputKeyClass(Text.class);job.setOutputValueClass(LongWritable.class);//5、设置job输入输出FileInputFormat.setInputPaths(job,new Path("file:///simple/maxmin.txt"));FileOutputFormat.setOutputPath(job,new Path("file:///simple/result"));//6 commit jobSystem.out.println(job.waitForCompletion(true) ? 0 : 1);;}
}