The Proxy Design Pattern is a structural design pattern that provides a surrogate or placeholder for another object to control access to it. This pattern is useful when you want to add an extra layer of control over access to an object. The proxy acts as an intermediary, controlling access to the real object¹.

Key Components

1. Subject: An interface or abstract class that defines the common interface shared by the RealSubject and Proxy classes. It declares the methods that the Proxy uses to control access to the RealSubject¹.

2. RealSubject: The actual object that the Proxy represents. It contains the real implementation of the business logic or the resource that the client code wants to access¹.

3. Proxy: Acts as a surrogate or placeholder for the RealSubject. It controls access to the real object and may provide additional functionality such as lazy loading, access control, or logging¹.

Example in Java