Can you explain the main differences between the Adapter, Facade, and Proxy patterns and in which situations it is better to use them?

Main differences between Adapter, Facade, and Proxy patterns:

• Adapter: Allows objects with incompatible interfaces to work together. It transforms the interface of one class into another interface expected by the client.

  • Used when integrating an existing class with a new interface.

• Facade: Provides a simplified interface to a complex subsystem, hiding its internal complexity.

  • Used to simplify interactions with a large number of classes.

• Proxy: Controls access to another object, possibly adding additional logic (e.g., lazy initialization, caching, security).

  • Used when managing access or adding behavior without modifying the original object.

Examples of situations:

• Adapter: integrating an old API with a new interface.
• Facade: providing a simple API for a complex library.
• Proxy: implementing lazy loading of a resource or access control.

Example of Adapter in Java:

interface Target {
    void request();
}

class Adaptee {
    void specificRequest() { System.out.println("Specific request"); }
}

class Adapter implements Target {
    private Adaptee adaptee = new Adaptee();
    public void request() {
        adaptee.specificRequest();
    }
}