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The Proxy and Facade patterns are structural design patterns in object-oriented programming, and they serve different purposes:

Proxy Pattern

• Purpose: The Proxy pattern provides a placeholder for another object to control access to it. It is often used to add a layer of security, lazy initialization, logging, or to manage resource-intensive objects.
• Example:

interface Image {

void display();

}

class RealImage implements Image {

private String fileName;

public RealImage(String fileName) { this.fileName = fileName; loadFromDisk();

}

private void loadFromDisk() {

System.out.println("Loading " + fileName);

}

public void display() {

System.out.println("Displaying " + fileName); }

}

class ProxyImage implements Image {

private RealImage realImage;

private String fileName;

public ProxyImage(String fileName) {

this.fileName = fileName; }

public void display() {

if (realImage == null) realImage = new RealImage(fileName); realImage.display();

}

}

Facade Pattern

• Purpose: The Facade pattern provides a simplified interface to a complex subsystem. It hides the complexities of the subsystem from the client, making the interface easier to use.
• Example:

class CPU {

public void start() { System.out.println("CPU started");

}

}

class Memory {

public void load() { System.out.println("Memory loaded"); }

}

class HardDrive {

public void readData() { System.out.println("Data read from hard drive");

}

}

class ComputerFacade {

private CPU cpu;

private Memory memory;

private HardDrive hardDrive;

public ComputerFacade() {

this.cpu = new CPU();

this.memory = new Memory();

this.hardDrive = new HardDrive();

}

public void startComputer() {

cpu.start();

memory.load();

hardDrive.readData();

} }

Summary:

• Proxy controls access to an object, often adding behavior before or after the actual object’s method execution.
• Facade simplifies interaction with a complex system by providing a unified, easy-to-use interface.