Introduction to DSA

🔹 Adapter Pattern in Object-Oriented Programming (OOP)

The **Adapter Pattern** is a **structural design pattern** that allows two incompatible interfaces to work together. It acts as a bridge between **two different systems** by translating one interface into another.

📌 Why Use the Adapter Pattern?

The Adapter Pattern helps in integrating **legacy code, third-party libraries, or different APIs** with your existing system.

✅ **Bridges Incompatible Interfaces** – Allows different systems to communicate.
✅ **Reusability** – Use existing code without modifying it.
✅ **Flexibility** – Makes your code more adaptable to changes.
✅ **Follows Open-Closed Principle** – Extends functionality without modifying existing code.

💡 Real-Life Example

Imagine a **laptop charger adapter** that allows a **European plug** to fit into an **American socket**. The adapter converts the plug type but keeps the functionality the same.

🖥️ Adapter Pattern in Java

Example of an adapter converting **old payment system** to a **new payment gateway**.


            interface NewPaymentGateway {
                void processPayment(double amount);
            }
            
            // Old payment system (Incompatible)
            class OldPaymentSystem {
                void makePayment(double amount) {
                    System.out.println("Payment of $" + amount + " processed using old system.");
                }
            }
            
            // Adapter to make old system work with new system
            class PaymentAdapter implements NewPaymentGateway {
                private OldPaymentSystem oldSystem;
            
                PaymentAdapter(OldPaymentSystem oldSystem) {
                    this.oldSystem = oldSystem;
                }
            
                public void processPayment(double amount) {
                    oldSystem.makePayment(amount);
                }
            }
            
            public class Main {
                public static void main(String[] args) {
                    OldPaymentSystem oldSystem = new OldPaymentSystem();
                    NewPaymentGateway adapter = new PaymentAdapter(oldSystem);
                    adapter.processPayment(100.0);
                }
            }

🖥️ Adapter Pattern in Python

Example of an adapter converting **legacy text format** to **modern JSON format**.


            class LegacyPrinter:
                def print_text(self, text):
                    return f"Legacy Printer: {text}"
            
            class JSONPrinterAdapter:
                def __init__(self, legacy_printer):
                    self.legacy_printer = legacy_printer
            
                def print_json(self, text):
                    return {"message": self.legacy_printer.print_text(text)}
            
            # Using the adapter
            legacy = LegacyPrinter()
            adapter = JSONPrinterAdapter(legacy)
            print(adapter.print_json("Hello, World!"))

🎯 Summary