public void write(DataOutput sortie) throws IOException
{
    sortie.writeLong(n);
    sortie.writeDouble(Sx);
    sortie.writeDouble(Sx2);
}

public void readFields(DataInput entree) throws IOException
{
    n = entree.readLong();
    Sx = entree.readDouble();
    Sx2 = entree.readDouble();
}