object is an instance of class (java)

System.out.print("Enter Room Number: ");
int a4 = scan.nextInt();
scan.nextLine();
booking[count]= new RoomBooking (a1,a2,a3,a4);
count++;

if (/* if the object is an instance of RoomBooking(subclass) */) {
    for (int y = 0; y < count; y++) {
        if (a4 == (((RoomBooking) booking[y]).getRoomNumber())) {
            System.out.print("Used number, Please Try again");
        }
    }
}

"if the object is an instance of RoomBooking(subclass)" How can i write that in java?

Sorry if that doesn't make sense, still learning.

If you need to know what's going on, there are 2 classes. Booking (normal Booking) and RoomBooking ( which extends Booking).. Since we have to create one array which stores a mixture of both, i need to check if the object(a4) is an instance of the RoomBooking so i can compare the numbers.

I have tried if ((RoomBooking.class.isInstance(a4))){...} but it didn't work.