🎓 Mastering Java in 2025 — The Complete Learning Path for Beginners to Pros!

Learning Java in 2025 is more exciting than ever. This guide covers everything — from writing your first HelloWorld to deploying scalable microservices with Spring Boot and exploring Java’s cutting-edge features like virtual threads and native image compilation with GraalVM.

Bookmark this guide! Each section below will eventually link to a deep-dive blog post. For now, use this page as your complete overview and roadmap.

• 📖 [1] Introduction to Java
• ⚙️ [2] Setting Up Java (JDK + IDE)
• 🔤 [3] Java Syntax & Basics
• 🧮 [4] Data Types & Variables
• 🔁 [5] Operators & Control Flow
• 📦 [6] Object-Oriented Programming in Java
• 🧰 [7] Classes, Objects, Constructors
• 🧠 [8] Inheritance & Polymorphism
• 🔒 [9] Encapsulation & Abstraction
• 🔀 [10] Interfaces & Abstract Classes
• 📚 [11] Java Collections Framework
• 🧵 [12] Multithreading & Concurrency
• 💾 [13] File I/O in Java
• 🎯 [14] Exception Handling
• 🌐 [15] Java Networking (Sockets, HTTP)
• 📈 [16] Streams, Lambdas & Functional Programming
• 🧪 [17] JUnit & Unit Testing
• 🌱 [18] Spring Boot — REST APIs
• 🚀 [19] Microservices with Spring Cloud
• 🔍 [20] JVM Internals
• ⚡ [21] Java in 2025 — GraalVM, Project Loom
• 🧱 [22] Java Design Patterns
• 💡 [23] Tips, Shortcuts & IDE Magic
• 🧠 [24] Java Interview Questions

📖 1. Introduction to Java

Java is a versatile, class-based, object-oriented language that has shaped enterprise computing since the mid-90s. Its philosophy? "Write Once, Run Anywhere." Java applications can run on any system with a JVM.

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⚙️ 2. Setting Up Java (JDK + IDE)

• Download and install the latest JDK (Java Development Kit).
• Install an IDE like IntelliJ IDEA or VS Code.
• Set JAVA_HOME and verify with java -version.

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🔤 3. Java Syntax & Basics

public class Hello {
  public static void main(String[] args) {
    System.out.println("Hello, Java!");
  }
}

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🧮 4. Data Types & Variables

• Primitive: int, float, double, char, boolean
• Non-primitive: String, Arrays, Classes
• Use var (since Java 10) for type inference

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🔁 5. Operators & Control Flow

• if, else, switch
• for, while, do-while
• break, continue

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📦 6. Object-Oriented Programming in Java

Java is built on the pillars of OOP: Abstraction, Encapsulation, Inheritance, Polymorphism.

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🧰 7. Classes, Objects, Constructors

class Car {
  String model;
  Car(String model) {
    this.model = model;
  }
}

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🧠 8. Inheritance & Polymorphism

Java allows code reuse through extends and overrides behavior using @Override.

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🔒 9. Encapsulation & Abstraction

Use private fields with public getters/setters. Abstract classes hide complexity.

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🔀 10. Interfaces & Abstract Classes

Java 8+ interfaces can have default methods. Abstract classes can't be instantiated.

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📚 11. Java Collections Framework

• List, Set, Map, Queue
• ArrayList vs LinkedList
• HashMap vs TreeMap

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🧵 12. Multithreading & Concurrency

Use Thread, Runnable, ExecutorService for concurrency.

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💾 13. File I/O in Java

Use File, BufferedReader, FileWriter. Java NIO offers better performance.

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🎯 14. Exception Handling

Use try-catch-finally, create custom exceptions.

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🌐 15. Java Networking (Sockets, HTTP)

Use Socket, ServerSocket, HttpClient.

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📈 16. Streams, Lambdas & Functional Programming

List<String> names = List.of("A", "B", "C");
names.stream().filter(n -> n.startsWith("A")).forEach(System.out::println);

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🧪 17. JUnit & Unit Testing

Use @Test, assertEquals in JUnit 5.

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🌱 18. Spring Boot — REST APIs

@RestController
public class ApiController {
  @GetMapping("/hello")
  public String hello() {
    return "Hello from API!";
  }
}

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🚀 19. Microservices with Spring Cloud

Break monoliths with Spring Cloud, Eureka, Zuul, and Docker/Kubernetes integration.

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🔍 20. JVM Internals

Understand bytecode, memory model, garbage collection strategies (G1, ZGC).

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⚡ 21. Java in 2025 — GraalVM, Project Loom

• GraalVM: Native images, polyglot capabilities
• Project Loom: Virtual threads (preview)

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🧱 22. Java Design Patterns

• Singleton, Factory, Strategy, Observer, Builder
• Best for system architecture and reusability

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💡 23. Tips, Shortcuts & IDE Magic

• Use psvm, sout shortcuts
• Live templates, refactor tools, and Git integration

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🧠 24. Java Interview Questions

• What’s the difference between abstract class and interface?
• Explain memory management in JVM.
• What is the diamond problem?

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— Blog by Aelify (ML2AI.com)

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