Database Reference
In-Depth Information
static class OldMaxTemperatureMapper
extends MapReduceBase
implements Mapper
<LongWritable, Text, Text, IntWritable> {
private static final int MISSING = 9999;
@Override
public void map(LongWritable key, Text value,
OutputCollector<Text, IntWritable> output, Reporter reporter
)
throws IOException {
String line = value.toString();
String year = line.substring(15, 19);
int airTemperature;
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]")) {
output.collect
(new Text(year), new IntWritable(airTemperature));
}
}
}
static class OldMaxTemperatureReducer
extends MapReduceBase
implements Reducer
<Text, IntWritable, Text, IntWritable> {
@Override
public void reduce(Text key,
Iterator
<IntWritable> values,
OutputCollector<Text, IntWritable> output, Reporter reporter
)
throws IOException {
int maxValue = Integer.MIN_VALUE;
while (
values.hasNext()
) {
maxValue = Math.max(maxValue,
values.next().get()
);
}
output.collect
(key, new IntWritable(maxValue));
}
}
public static void main(String[] args) throws IOException {
if (args.length != 2) {
System.err.println("Usage: OldMaxTemperature <input path> <output
path>");
