public void add(IntArrayWritable autre)
{
    // récupérer les valeurs
    Writable[] values = this.get();
    Writable[] autres = autre.get();

    // this = this + autre
    for (int i=0; i<values.length; i++) {
        IntWritable val = (IntWritable)values[i];
        IntWritable aut = (IntWritable)autres[i];
        val.set(val.get() + aut.get());
    }
}