Core Java ☕

A structured repository for learning, revising, and practicing Core Java from the ground up. This repository is designed with a backend development mindset and serves as a reference while preparing for Java interviews and Spring Boot.

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🎯 Objectives

• Build a strong foundation in Core Java
• Understand Java syntax and language features
• Master Object-Oriented Programming
• Practice the Java Collections Framework
• Learn Java 8 features used in modern backend development
• Prepare for Spring Boot and backend engineering
• Maintain well-organized revision notes and code examples

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📂 Project Structure

core-java/
│
├── src/
│   └── com/
│       └── yusuf/
│           ├── Main.java
│           ├── basics/
│           ├── controlflow/
│           ├── methods/
│           ├── arrays/
│           ├── strings/
│           ├── oops/
│           ├── exceptions/
│           ├── collections/
│           ├── generics/
│           ├── java8/
│           ├── filehandling/
│           ├── multithreading/
│           ├── memory/
│           ├── advanced/
│           ├── interview/
│           └── projects/

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📚 Topics Covered

Basics

• Variables
• Data Types
• Operators
• Type Casting
• User Input
• Output Formatting

Control Flow

• if-else
• switch
• for loop
• while loop
• do-while loop
• break & continue

Methods

• Methods
• Method Overloading
• Variable Arguments (VarArgs)
• Recursion

Arrays

• One-Dimensional Arrays
• Multi-Dimensional Arrays
• Array Operations

Strings

• String
• StringBuilder
• StringBuffer
• Common String Operations

Object-Oriented Programming

• Classes & Objects
• Constructors
• this Keyword
• static Keyword
• Encapsulation
• Inheritance
• Polymorphism
• Abstraction
• Interfaces
• Packages

Exception Handling

• try-catch
• finally
• throw
• throws
• Custom Exceptions

Collections Framework

• List
• Set
• Queue
• Map
• Iterator
• Comparable
• Comparator

Generics

• Generic Classes
• Generic Methods
• Wildcards

Java 8

• Lambda Expressions
• Functional Interfaces
• Streams API
• Method References
• Optional
• Date & Time API

File Handling

• File
• FileReader
• FileWriter
• BufferedReader
• BufferedWriter
• Serialization

Multithreading

• Thread
• Runnable
• Synchronization
• ExecutorService
• Callable
• Future

JVM & Memory

• Stack vs Heap
• Garbage Collection
• String Pool
• Object Lifecycle

Advanced Java

• Enums
• Annotations
• Reflection
• Inner Classes
• Records
• Sealed Classes

Interview

Frequently asked Java interview programs and conceptual questions.

Projects

Small console-based Java projects to apply learned concepts.

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🚀 How to Run

1. Clone the repository.
2. Open it in IntelliJ IDEA.
3. Navigate to the desired package.
4. Run the corresponding Java class containing the main() method.

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📌 Learning Strategy

Each Java concept is placed in its own package and class to keep the code modular, easy to understand, and convenient for revision. The repository is intended to grow alongside the learning journey, with clean examples and practical implementations.

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🛠 Tech Stack

• Java
• IntelliJ IDEA
• Git
• GitHub

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📈 Progress

• Basics
• Control Flow
• Methods
• Arrays
• Strings
• OOP
• Exception Handling
• Collections
• Generics
• Java 8
• File Handling
• Multithreading
• JVM & Memory
• Advanced Java
• Mini Projects

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📄 License

This repository is maintained for educational purposes and continuous learning.