☕ Java Language Mastery – Complete Core to Advanced Guide

A comprehensive Java learning repository covering core fundamentals, modern Java features, JVM internals, functional programming, concurrency, and performance basics.
This repository is designed as a structured reference + practice archive for mastering Java from beginner to advanced level using modern JDK standards (Java 8 → Java 17+).

---

📌 Repository Goals

• Build strong Java fundamentals
• Understand modern Java features
• Practice clean, idiomatic Java
• Prepare for interviews, real-world projects, and backend frameworks
• Serve as a long-term Java reference repository

---

🧱 Java Language Mastery Index

---

I. Foundational Syntax & Structure

• Main method & program structure
• Variables: declaration, initialization, scope
• Primitive data types
• Reference vs primitive types
• Operators (arithmetic, logical, bitwise, ternary)
• Control flow:
  • if, if-else, switch (enhanced switch)
  • for, enhanced for-loop, while, do-while
  • break, continue, return

---

II. Object-Oriented Programming (OOP)

• Classes & objects
• Methods & method overloading
• Constructors (default & parameterized)
• this keyword
• Access modifiers
• OOP pillars:
  • Encapsulation
  • Inheritance
  • Polymorphism
  • Abstraction
• Interfaces (default, private, static methods)
• Records (Java 16+)
• Sealed classes & interfaces (Java 17+)

---

III. Core APIs & Memory Management

• String, immutability & performance
• StringBuilder & StringBuffer
• Arrays (1D & multi-dimensional)
• Packages & import
• Java Memory Model (Stack vs Heap)
• Garbage Collection fundamentals

---

IV. Exception Handling

• Error vs Exception
• Checked vs unchecked exceptions
• try-catch-finally
• Try-with-resources
• throw keyword
• Custom exceptions

---

V. Collections Framework

Core Interfaces

• Collection, List, Set, Queue, Map

Implementations

• List: ArrayList, LinkedList
• Set: HashSet, LinkedHashSet, TreeSet
• Queue: PriorityQueue, ArrayDeque
• Map: HashMap, LinkedHashMap, TreeMap

Advanced Concepts

• equals() & hashCode() contract
• Comparable & Comparator
• Concurrent collections

---

VI. Generics

• Generic classes & methods
• Bounded type parameters
• Diamond operator (<>)
• Wildcards:
  • ? extends
  • ? super
  • Unbounded ?

---

VII. Functional Programming (Java 8+)

• Lambda expressions
• Functional interfaces:
  • Predicate
  • Function
  • Supplier
  • Consumer
• Method references
• Optional
• Stream API:
  • Creation
  • Intermediate operations
  • Terminal operations
  • Parallel streams

---

VIII. Concurrency & Multithreading

• Thread creation (Thread vs Runnable)
• ExecutorService
• Synchronization & intrinsic locks
• volatile
• Explicit locks:
  • ReentrantLock
  • ReadWriteLock
• High-level concurrency:
  • Callable & Future
  • CompletableFuture
• Concurrent vs synchronized collections

---

IX. Modern I/O & Data Handling

• Java Date & Time API (java.time)
• File handling with NIO.2 (Path, Files, Paths)

---

X. Advanced Topics & JVM Internals

• Annotations (built-in & custom)
• Reflection
• Classloading basics
• Java Modules (JPMS)
• JVM tuning basics (-Xms, -Xmx)
• JVM architecture overview

---

🛠️ Tech Stack

• Language: Java (8 → 17+)
• Build Tool: Maven / Gradle (optional)
• IDE: IntelliJ IDEA / Eclipse / VS Code
• Style: Clean, readable, best-practice Java

---

🎯 Who This Repository Is For

• Java beginners building strong foundations
• Intermediate developers leveling up
• Backend developers preparing for Spring Boot
• Interview preparation (Core Java + Advanced)
• Anyone wanting a modern Java reference

---

🚀 How to Use

git clone https://github.com/variables-dev-coder/Core_Java_Practice.git
cd Core_Java_Practice


---


> ⭐ Star this repo if you're also learning Java or preparing for interviews. Let's grow and learn together!