MaxTemperatureMapper.java

package examples.mapred.temperature;

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;

public class MaxTemperatureMapper extends
		Mapper<LongWritable, Text, Text, IntWritable> {
	private static final int MISSING = 9999;

	@Override
	public void map(LongWritable key, Text value, Context context)
			throws IOException, InterruptedException {
		String line = value.toString();
		String year = line.substring(15, 19);
		int airTemperature;
		try {
			if (line.charAt(87) == '+') { // parseInt doesn't like leading
											// plus
											// signs
				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));
			}
		} catch (NumberFormatException e) {
		}
	}
}