Demo.java

public class Main {

    public static void main(String[] args) throws Exception {

        final TicketManager tm = new TicketManager();

        Thread t1 = new Thread(new Runnable() {

            public void run() {

                tm.purchaseTickets(90);

            }
        });
        t1.start();
        tm.purchaseTickets(60);
    }
}