Java Tutorial

1. Java Introduction

What Java is, why it still runs a huge share of the world's backend systems, and how the JVM, JDK and JRE fit together.

2. Install Java (JDK)

Install a modern JDK (21 LTS), verify the install, and compile and run your first program from the command line.

3. Java Syntax & Variables

Java program structure, the main method, variables, primitive types, and type inference with var.

4. Operators & Control Flow

Arithmetic, comparison and logical operators, if/else, switch expressions, and for/while loops in Java.

5. Classes, Objects & Inheritance

Classes, constructors, encapsulation, inheritance, interfaces and polymorphism in Java.

6. Collections & Streams

List, Set and Map, generics, and the Streams API for filtering, mapping and reducing data.

7. Exception Handling & Multithreading

try/catch/finally, custom exceptions, threads, the Executor framework, and thread-safety basics.

8. Streams Performance & Parallel Streams

How a stream pipeline really executes, Spliterators, when parallelStream() helps or hurts, and a benchmarked before/after example.

9. JVM Memory Model & Garbage Collection

Heap generations, a survey of GC algorithms (G1, ZGC), what really causes OutOfMemoryError, and reading a GC log.

10. Java Interview Questions

Commonly asked Java interview questions with clear, practical answers.