Why is Java Observer deprecated?

Ans: The Observable class and the Observer interface have been deprecated in Java 9 because the event model supported by Observer and Observable is quite limited, the order of notifications delivered by Observable is unspecified, and state changes are not in one-for-one correspondence with notifications.

Read more

How does the visitor pattern work?

The Visitor pattern represents an operation to be performed on the elements of an object structure without changing the classes on which it operates . This pattern can be observed in the operation of a taxi company. When a person calls a taxi company (accepting a visitor), the company dispatches a cab to the customer.

Read more