java Singleton - prevent multiple creation through reflection

Question

I have a singleton like this.

public class BookingFactory {

    private final static BookingFactory instance;

    static {
        instance = new BookingFactor         


        

Answer 1

Make the assertion in the constructor:

private BookingFactory() {
    if (instance != null)
        throw new IllegalStateException("Only one instance may be created");
    System.out.println("Object is created.");
}