Hadoop学习之第四章节：最高温度统计测试程序

1.测试温度数据下载：

http://down.51cto.com/data/2213610

2.将数据上传到hdfs中

3.测试代码为：

MinTemperature

import org.apache.hadoop.fs.Path;import org.apache.hadoop.io.IntWritable;import org.apache.hadoop.io.Text;import org.apache.hadoop.mapreduce.Job;import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat; publicclass MinTemperature {       publicstaticvoid main(String[] args) throws Exception {        if(args.length != 2) {            System.err.println("Usage: MinTemperature 
");            System.exit(-1);        }               Job job = new Job();        job.setJarByClass(MinTemperature.class);        job.setJobName("Min temperature");        FileInputFormat.addInputPath(job, new Path(args[0]));        FileOutputFormat.setOutputPath(job, new Path(args[1]));        job.setMapperClass(MinTemperatureMapper.class);        job.setReducerClass(MinTemperatureReducer.class);        job.setOutputKeyClass(Text.class);        job.setOutputValueClass(IntWritable.class);        System.exit(job.waitForCompletion(true) ? 0 : 1);    }}

MinTemperatureMapper

import java.io.IOException;import org.apache.hadoop.io.IntWritable;import org.apache.hadoop.io.LongWritable;import org.apache.hadoop.io.Text;import org.apache.hadoop.mapreduce.Mapper; publicclass MinTemperatureMapper extends Mapper{     privatestatic final intMISSING = 9999;       @Override    publicvoid map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {               String line = value.toString();        String year = line.substring(15, 19);               int airTemperature;        if(line.charAt(87) == '+') {            airTemperature = Integer.parseInt(line.substring(88, 92));        } else {            airTemperature = Integer.parseInt(line.substring(87, 92));        }               String quality = line.substring(92, 93);        if(airTemperature != MISSING && quality.matches("[01459]")) {            context.write(new Text(year), new IntWritable(airTemperature));        }    }}

MinTemperatureReducer

import java.io.IOException;import org.apache.hadoop.io.IntWritable;import org.apache.hadoop.io.Text;import org.apache.hadoop.mapreduce.Reducer; publicclass MinTemperatureReducer extends Reducer {     @Override    publicvoid reduce(Text key, Iterable values, Context context) throws IOException, InterruptedException {               int minValue = Integer.MAX_VALUE;        for(IntWritable value : values) {            minValue = Math.min(minValue, value.get());        }        context.write(key, new IntWritable(minValue));    }}