This repository contains my learning and hands-on implementations of core object-oriented design patterns and principles in Java.
The goal of this project is to deeply understand how modern frameworks like Spring work internally by implementing these concepts from scratch.

Ensures that a class has only one instance and provides a global access point to it.

Key concepts learned:

• Private constructor
• Static instance
• Lazy initialization
• Object identity (==)
• Thread-safety considerations

Dependency Injection removes tight coupling by injecting dependencies instead of creating them directly.

Key concepts learned:

• Programming to interfaces
• Constructor-based injection (recommended)
• Loose coupling
• Testability and flexibility

Encapsulates object creation logic and allows the client to request objects without knowing their concrete classes.

Key concepts learned:

• Centralized object creation
• Open–Closed Principle
• Replacing new with factories
• Runtime object selection

what does “Inversion of Control” even mean?
Normally your code controls object creation and flow, With IoC the framework controls object creation and flow
👉 The control is inverted From you → to the container
That’s it. That’s IoC.

• Creates objects
• Decides which implementation to use
• Injects dependencies
• Controls object wiring This mimics how Spring’s ApplicationContext works internally.