public class AlertServer {
    
    private AlertListener[] clients;
    private int numberOfClients;
    
    public AlertServer(int capacity) {
        clients = new AlertListener[capacity];
        numberOfClients = 0;
    }
    
    public void register(AlertListener client) {
        clients[numberOfClients] = client;
        numberOfClients++;
    }
    
    public void broadcast(String message) {
        for (int i=0; i<numberOfClients; i++) {
            clients[i].processAlert(message);
        }
    }
}