Java util

Observer is a behavioral design pattern . It specifies communication between objects: observable and observers. An observable is an object which notifies observers about the changes in its state. For example, a news agency can notify channels when it receives news.15 May 2021

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.

An Observable is simply a collection of data that waits to be invoked (subscribed) before it can emit any data . If you’ve worked with promises, then the way to access the data is to chain it with the then() operator or use the ES6 async/await .

Observable is used to create subclasses that other parts of the program can observe . When an object of such subclass undergoes a change, observing classes are notified. The update( ) method is called when an observer is notified of a change.8 Tem 2017