What is Observer pattern in Java?

Disadvantages of Observer Design Pattern The main disadvantage of the observer design pattern that subscribers are notified in random order . There is also a memory leakage problem in the observer design pattern because of the observer’s explicit register and unregistering.

Subject in the Observer pattern has three tasks: i) Provide methods to register and remove observer. ii) Maintains a list of its observers/subscribers. iii) And notify them automatically when any state changes .

What Is the Observer Pattern? 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

Observer pattern is used when there is one-to-many relationship between objects such as if one object is modified, its depenedent objects are to be notified automatically . Observer pattern falls under behavioral pattern category.