public class TraitementReducer
        extends Reducer<TypCleI,TypValI, TypCleS,TypValS>
{
    @Override
    public void reduce(TypCleI cleI, Iterable<TypValI> listeI,
                Context context) throws Exception
    {
        TypCleS cleS = new TypCleS();
        TypValS valS = new TypValS();
        for (TypValI val: listeI) {
            /** traitement: cleS.set(...), valS.set(...) **/
        }
        context.write(cleS, valS);
    }
}