1️⃣ Singleton Pattern — Subheadings

• Introduction: Why Do We Need Singleton?
• What is Singleton Pattern?
• Core Idea Behind Singleton
• Basic Java Implementation
• Thread Safety Concerns
• Production-Ready Implementation (Best Practice)
• Real-World Use Cases
• Advantages
• Drawbacks & Limitations
• When NOT to Use Singleton
• Interview Questions & Key Takeaways
• Final Thoughts

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🏭 2️⃣ Factory Pattern — Subheadings

• Introduction: The Problem with Direct Object Creation
• What is Factory Pattern?
• When Should You Use It?
• Step-by-Step Java Implementation
• How It Improves Maintainability
• Real-World Examples (Spring, Logging, JDBC)
• Factory vs Constructor
• Advantages
• Limitations
• When NOT to Use Factory
• Interview Questions & Key Takeaways
• Final Thoughts

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🎯 3️⃣ Strategy Pattern — Subheadings

• Introduction: The Problem with Multiple If-Else Conditions
• What is Strategy Pattern?
• Core Idea: Encapsulating Behavior
• Step-by-Step Java Implementation
• How It Supports Open/Closed Principle
• Real-World Examples (Comparator, Payment Systems)
• Strategy vs Factory
• Advantages
• Drawbacks
• When NOT to Use Strategy
• Interview Questions & Key Takeaways
• Final Thoughts

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👀 4️⃣ Observer Pattern — Subheadings

• Introduction: Managing Dependent Objects
• What is Observer Pattern?
• Core Components (Subject & Observer)
• Step-by-Step Java Implementation
• How It Enables Loose Coupling
• Real-World Examples (Event Systems, Spring Events)
• Observer vs Pub-Sub (Optional Advanced Section)
• Advantages
• Drawbacks (Memory Leaks, Performance Issues)
• When NOT to Use Observer
• Interview Questions & Key Takeaways
• Final Thoughts

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🎨 5️⃣ Decorator Pattern — Subheadings

• Introduction: Extending Behavior Without Modifying Code
• What is Decorator Pattern?
• Core Idea: Wrapping Objects
• Step-by-Step Java Implementation
• How It Prevents Subclass Explosion
• Real-World Examples (Java I/O Streams)
• Decorator vs Strategy
• Advantages
• Drawbacks
• When NOT to Use Decorator
• Interview Questions & Key Takeaways
• Final Thoughts

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🏗 6️⃣ Builder Pattern — Subheadings

• Introduction: The Problem with Telescoping Constructors
• What is Builder Pattern?
• Core Idea: Step-by-Step Object Construction
• Step-by-Step Java Implementation
• How It Improves Readability & Immutability
• Real-World Examples (Lombok @Builder, Spring Config)
• Builder vs Factory
• Advantages
• Limitations
• When NOT to Use Builder
• Interview Questions & Key Takeaways
• Final Thoughts