Hadoop入门进阶课程5--MapReduce原理及操作 (4)

10.  运行每一个任务；

下载气象数据集部分数据，写一个Map-Reduce作业，求每年的最低温度

1 import org.apache.hadoop.fs.Path; 2 import org.apache.hadoop.io.IntWritable; 3 import org.apache.hadoop.io.Text; 4 import org.apache.hadoop.mapreduce.Job; 5 import org.apache.hadoop.mapreduce.lib.input.FileInputFormat; 6 import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat; 7 8 public class MinTemperature { 9 10 public static void main(String[] args) throws Exception { 11 if(args.length != 2) { 12 System.err.println("Usage: MinTemperature<input path> <output path>"); 13 System.exit(-1); 14 } 15 16 Job job = new Job(); 17 job.setJarByClass(MinTemperature.class); 18 job.setJobName("Min temperature"); 19 FileInputFormat.addInputPath(job, new Path(args[0])); 20 FileOutputFormat.setOutputPath(job, new Path(args[1])); 21 job.setMapperClass(MinTemperatureMapper.class); 22 job.setReducerClass(MinTemperatureReducer.class); 23 job.setOutputKeyClass(Text.class); 24 job.setOutputValueClass(IntWritable.class); 25 System.exit(job.waitForCompletion(true) ? 0 : 1); 26 } 27 }