Pour faire la comparaison des String, tu n'as qu'à utiliser la méthode de String compareTo()
Citer:
Returns:
the value 0 if the argument string is equal to this string; a value less than 0 if this string is lexicographically less than the string argument; and a value greater than 0 if this string is lexicographically greater than the string argument.
Donc,
if (paramTableau[position].getCote().compareTo( paramTableau[position+1].getCote() > 0)