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 extends
Mapper<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);
@Override
protected 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;
@Override
protected 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 type
job.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 job
System.out.println(job.waitForCompletion(true) ? 0 : 1);;
}
}
本图文内容来源于网友网络收集整理提供,作为学习参考使用,版权属于原作者。
THE END
二维码