Java Learning Path - From Basic to Advanced

A comprehensive collection of Java programs covering fundamental to advanced concepts. Each file is a standalone program demonstrating specific Java features.

📚 Learning Path

Basics (Files 01-09)

1. 01-HelloWorld.java - First program, basic structure
2. 02-Variables-DataTypes.java - Data types, variables, constants
3. 03-Input-Output.java - Scanner, formatted output
4. 04-Operators.java - Arithmetic, logical, bitwise operators
5. 05-ControlFlow.java - if-else, switch statements
6. 06-Loops.java - for, while, do-while, enhanced for
7. 07-Methods.java - Method declaration, overloading, recursion
8. 08-Arrays.java - Arrays, multidimensional arrays, Arrays class
9. 09-Strings.java - String operations, StringBuilder

Object-Oriented Programming (Files 10-13)

10. 10-OOP-Classes.java - Classes, objects, constructors, encapsulation
11. 11-OOP-Inheritance.java - Inheritance, super keyword
12. 12-OOP-Polymorphism.java - Method overriding, runtime polymorphism
13. 13-Abstract-Interface.java - Abstract classes, interfaces

Collections & Advanced (Files 14-18)

14. 14-Collections-ArrayList.java - ArrayList operations
15. 15-Collections-HashMap.java - HashMap, key-value pairs
16. 16-ExceptionHandling.java - try-catch, custom exceptions
17. 17-FileIO.java - File reading/writing, BufferedReader/Writer
18. 18-Generics.java - Generic classes, methods, bounded types

Modern Java (Files 19-25)

19. 19-Lambda-Streams.java - Lambda expressions, Stream API
20. 20-Multithreading.java - Threads, Runnable, synchronization
21. 21-Enums.java - Enumerations, enum with methods
22. 22-Annotations.java - Built-in and custom annotations
23. 23-Reflection.java - Reflection API, dynamic class inspection
24. 24-DesignPatterns.java - Singleton, Factory, Builder patterns
25. 25-Optional.java - Optional class for null safety

🚀 How to Use

Compile and Run

# Compile a single file
javac 01-HelloWorld.java

# Run the compiled class
java HelloWorld

# Compile and run in one step (Java 11+)
java 01-HelloWorld.java

Learning Approach

1. Start from 01-HelloWorld.java and progress sequentially
2. Read the code comments for explanations
3. Compile and run each program
4. Modify the code to experiment
5. Move to the next file once comfortable

📖 Topics Covered

• Fundamentals: Variables, operators, control flow, loops
• Methods: Declaration, overloading, recursion, varargs
• Data Structures: Arrays, ArrayList, HashMap, Strings
• OOP: Classes, inheritance, polymorphism, abstraction, interfaces
• Collections Framework: ArrayList, HashMap, iteration
• Exception Handling: try-catch-finally, custom exceptions
• File I/O: Reading/writing files, BufferedReader/Writer
• Generics: Type-safe collections and methods
• Modern Java: Lambda expressions, Streams, Optional
• Concurrency: Multithreading, synchronization
• Advanced: Enums, Annotations, Reflection, Design Patterns

💡 Tips

• Each file is self-contained and can be compiled independently
• Class name must match the filename (e.g., HelloWorld.java contains class HelloWorld)
• Files 01-18 cover core Java concepts
• Files 19-25 require Java 8 or later for modern features
• Practice by modifying examples and creating your own variations

🔧 Requirements

• JDK 8 or later (Java Development Kit)
• Text editor or IDE (VS Code, IntelliJ IDEA, Eclipse)
• Command line or terminal

📝 Compilation Notes

• Java is case-sensitive
• Each public class must be in its own file
• File name must match the public class name
• Use javac to compile, java to run

Happy Learning! 🎓