[1. Class](https://firstcode.school/java-objects-and-classes/)

2. Object

[3. Constructor](https://techvidvan.com/tutorials/java-constructor/)

[4. Inheritance](https://data-flair.training/blogs/inheritance-in-java/)

5. Polymorphism

[6. Encapsulation](https://techvidvan.com/tutorials/java-encapsulation/)

7. Abstraction

[8. Interface](https://firstcode.school/interface-in-java-with-examples/)

9. Package

10. Method

11. Variable

12. Data Type

13. Array

14. Loop (for, while, do-while)

15. Conditional Statements (if, else, switch)

[16. Exception Handling](https://data-flair.training/blogs/exception-handling-in-java/)

17. Try-Catch Blocks

18. Finally Block

19. Throw and Throws

[20. Static Keyword](https://www.youtube.com/watch?v=B_uSj1XNyYw)

[21. Final Keyword](https://www.youtube.com/watch?v=ZxlnpumhQ6o)

22. Abstract Class

[23. Interface](https://www.youtube.com/watch?v=vkG5hfPljSc)

24. Method Overloading

[25. Method Overriding](https://techvidvan.com/tutorials/java-method-overriding/)

26. Access Modifiers (public, private, protected, default)

27. Packages and Import

28. Collection Framework (List, Set, Map, etc.)

29. Generics

[30. Lambda Expressions](https://data-flair.training/blogs/java-functional-interface/)

31. Streams API

[32. File Handling](https://www.youtube.com/watch?v=NCCyXwFQiNw)

[33. Multithreading](https://www.youtube.com/watch?v=Tj6zjgpVO-A)

34. Synchronization

35. Thread Pools

36. Networking (Socket, ServerSocket)

[37. JDBC (Java Database Connectivity)](https://www.youtube.com/watch?v=9brA8j7nndI)

38. GUI Programming (Swing, JavaFX)

39. Event Handling

40. JUnit (for Unit Testing)

41. Annotations (e.g., @Override, @Deprecated)

42. Enums

43. Reflection

44. Serialization

[45. Garbage Collection](https://techvidvan.com/tutorials/java-garbage-collection/)

46. Java Virtual Machine (JVM)

47. Memory Management

48. Concurrency Utilities (e.g., Executors)

49. Big-O Notation (for algorithmic complexity)

50. Design Patterns (e.g., Singleton, Observer, Factory)

These concepts form the foundation of Java programming and are essential for building robust and scalable applications.

This section will explore the fundamental principles of Object-Oriented Programming (OOP) without delving into code. Object-Oriented Programming is a paradigm that revolves around the concept of "objects," encapsulating data and behaviour into cohesive units.