public class MedianeLongueurLignesEtape1Reducer
    extends Reducer<IntWritable, LongWritable,
                    IntWritable, LongWritable> {
    @Override
    public void reduce(IntWritable cleI,
               Iterable<LongWritable> valeursI, Context context)
            throws IOException, InterruptedException {
        long nombre = 0L;
        for (LongWritable valeurI : valeursI) {
            nombre += valeurI.get();
        }
        LongWritable valeurS = new LongWritable(nombre);
        context.write(cleI, valeurS);
    }
}