📌 Advanced Java Lab - Assignments (UCSH-605)

This folder contains all the assignments for the Advanced Java Lab (UCSH-605) course, focusing on SOLID principles, Object-Oriented Design, and Java Coding practices.

---

📜 List of Assignments

Assignment	Description	Topics Covered
Assignment 1	Refactor a Poorly Designed Code (Apply SRP & OCP)	Single Responsibility Principle (SRP), Open/Closed Principle (OCP)
Assignment 2	Implement Liskov Substitution Principle (LSP)	Liskov Substitution Principle (LSP), Class Hierarchy Design
Assignment 3	Payment Processing System (Applying All SOLID Principles)	SOLID Principles, Interface Segregation, Dependency Inversion
Assignment 4	Chat App using Socket Programming in Java	1) One-to-One 2) One-to-Many

---

🔹 Assignment 1: Refactor a Poorly Designed Code (SRP & OCP)

📌 Problem Statement

The given Java code violates SRP (Single Responsibility Principle) and OCP (Open/Closed Principle).
Refactor the code to:

1. Separate concerns properly (SRP)
2. Make it extensible for new storage types without modifying the base class (OCP)

📌 Files

• easy1.java Original code violating SOLID principles → Refactored version following SRP & OCP.

📌 Topics Covered

✅ Single Responsibility Principle (SRP) – Ensure each class has a single responsibility.
✅ Open/Closed Principle (OCP) – Allow extension without modifying existing code.

---

🔹 Assignment 2: Implement Liskov Substitution Principle (LSP)

📌 Problem Statement

A Penguin class extends Bird, but Bird has a fly() method. This violates LSP because not all birds can fly.

📌 Task

1. Identify the issue in the hierarchy.
2. Refactor the design to follow LSP.
3. Ensure subclasses can replace the base class without breaking behavior.

📌 Files

• easy2.java
  • Before Refactoring → Penguin inherits fly(), violating LSP.
  • After Refactoring → Introduces Bird as an abstract class and CanFly interface.

📌 Topics Covered

✅ Liskov Substitution Principle (LSP) – Subclasses must be replaceable without altering system correctness.
✅ Proper Class Hierarchy Design – Use abstraction to define capabilities correctly.

---

🔹 Assignment 3: Design a Payment Processing System (SOLID)

📌 Problem Statement

Create a scalable and maintainable payment processing system supporting:

• Credit Card
• PayPal
• Google Pay

📌 Requirements

✅ Follow SOLID Principles
✅ Allow adding new payment methods without modifying existing code
✅ Use dependency injection for flexibility

📌 Class Structure

PaymentService (Interface)
   ├── CreditCardPayment (Implements PaymentService)
   ├── PayPalPayment (Implements PaymentService)
   ├── GooglePayPayment (Implements PaymentService)
PaymentProcessor
PaymentLogger
PaymentServiceManager
Main

📌 Files

diffass3.java Implements all SOLID principles in a payment system.

📌 Topics Covered

✅ Single Responsibility Principle (SRP) – Separate payment processing, logging, and transaction handling.
✅ Open/Closed Principle (OCP) – Allow new payment methods without modifying existing code.
✅ Liskov Substitution Principle (LSP) – Ensure each payment method behaves correctly as a PaymentService.
✅ Interface Segregation Principle (ISP) – Keep interfaces minimal and focused.
✅ Dependency Inversion Principle (DIP) – Depend on abstractions (PaymentService), not concrete implementations.

how_to_run: steps:

- step: Clone the repository
  command: |
    git clone https://github.com/Saiganesh224212/Advanced_Java_Lab.git

- step: Compile Java files
  commands:
    - javac easy1.java
    - javac easy2.java
    - javac diffass3.java

- step: Run Java programs
  commands:
    - java easy1
    - java easy2
    - java diffass3

🔹 Assignment 4: Design a Chat App using Sockets in JAVA