735 ILCS 5/2-801: Prerequisites for the maintenance of a class action.

An action may be maintained as a class action in any court of this State and a party may sue or be sued as a representative party of the class only if the court finds:

(1) The class is so numerous that joinder of all members is impracticable.

(2) There are questions of fact or law common to the class, which common questions predominate over any questions affecting only individual members.

(3) The representative parties will fairly and adequately protect the interest of the class.

(4) The class action is an appropriate method for the fair and efficient adjudication of the controversy.