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Observer Pattern Tutorial with Example in Java

Introduction :

The Observer Pattern is a behavioral design pattern where an object, known as the subject, maintains a list of dependents, known as observers, that are notified of any state changes. This pattern is widely used to implement distributed event handling systems.

Let’s walk through a simple example of the Observer Pattern in Java.

Step 1: Define the Subject Interface

Step 2: Implement the Concrete Subject

Step 3: Define the Observer Interface

Step 4: Implement Concrete Observers

Step 5: Test the Observer Pattern

In this example, the ConcreteSubject maintains a list of observers and notifies them whenever its state changes. The ConcreteObserver objects register with the subject and receive updates when the state changes.

This is a basic example, and in real-world scenarios, the Observer Pattern is used in various applications such as event handling frameworks, UI components, and more. It promotes loose coupling between the subject and observers, making the system more modular and maintainable.

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