MAXTEMP

import java.io.IOException;import org.apache.hadoop.conf.Configuration;import org.apache.hadoop.fs.Path;import org.apache.hadoop.io.IntWritable;import org.apache.hadoop.io.LongWritable;import org.apache.hadoop.io.Text;import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;import org.apache.hadoop.mapreduce.Job;import org.apache.hadoop.mapreduce.Mapper;import org.apache.hadoop.mapreduce.Reducer;import org.apache.hadoop.util.GenericOptionsParser;public class MaxTemp{public static class NcdcParser {private static final int MISSING_TEMPERATURE = 9999;private String year;private int airTemperature;private String quality;public void parse(String record){    year = record.substring(15,19);    String airTemperatureString;    if(record.charAt(87)== '+'){        airTemperatureString = record.substring(88,92);    }else{        airTemperatureString = record.substring(87,92);    }    airTemperature = Integer.parseInt(airTemperatureString);    quality = record.substring(92,93);}public void parse(Text record){    parse(record.toString());}public boolean isValidTemperature(){    return airTemperature !=MISSING_TEMPERATURE && quality.matches("[01459]");}public String getYear(){    return year;}public int getAirTemperature(){    return airTemperature;}}public static class MaxTemperatureMapper extendsMapper<LongWritable, Text, Text, IntWritable> {private NcdcParser parser = new NcdcParser();public void map(LongWritable key,Text value,Context context){parser.parse(value);if(parser.isValidTemperature()){    try {       context.write(new Text(parser.getYear()), new IntWritable(parser.getAirTemperature()));    } catch (IOException e) {       e.printStackTrace();    } catch (InterruptedException e) {       e.printStackTrace();    }}}}public static class MaxTemperatureReducer extends Reducer<Text, IntWritable, Text, IntWritable> {private IntWritable result = new IntWritable();public void reduce(Text key,Iterable<IntWritable> values,Context context) throws IOException, InterruptedException{int maxValue = Integer.MIN_VALUE;for(IntWritable value : values){    maxValue = Math.max(maxValue, value.get());}result.set(maxValue);context.write(key,result);}}public static void main(String[] args) throws Exception { Configuration conf = new Configuration(); conf.set("mapred.job.tracker", "192.168.1.23:9001");    String[] otherArgs = new GenericOptionsParser(conf, args).getRemainingArgs();    if (otherArgs.length != 2) {      System.err.println("Usage: MaxTemperature <in> <out>");      System.exit(2);    }    Job job = new Job(conf, "Max temperature");    job.setJarByClass(MaxTemp.class);    job.setMapperClass(MaxTemperatureMapper.class);    job.setCombinerClass(MaxTemperatureReducer.class);    job.setReducerClass(MaxTemperatureReducer.class);        FileInputFormat.addInputPath(job, new Path(args[0]));    FileOutputFormat.setOutputPath(job, new Path(args[1]));        job.setOutputKeyClass(Text.class);    job.setOutputValueClass(IntWritable.class);    System.exit(job.waitForCompletion(true) ? 0 : 1);    }}