hadoop|MapReduce实验——计算整数的最大值最小值 hadoop|big|data|mapreduce

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 { //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 { //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 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); ; } }