Complete Java Learning Guide: Beginner to Advanced

This page is the home base for a long Java series. Each chapter is meant to be its own article: one main idea, slow explanation, examples, mistakes, habits, and a tiny exercise.

All 151 chapters of this guide are on the blog—Parts 1–17, from first programs through Spring Boot, advanced JVM topics, security and production, and a closing roadmap (Chapters 1–151). The order is fixed; titles may still be tweaked slightly over time. Use this index to see the full arc, then circle back when your projects need depth. Depth beats speed.

Beginner tip: bookmark this page. When a new chapter goes live, open it from here so you do not skip foundations.

Published chapters (links)

Full chapter outline (1–151)

Below is the full roadmap. Every chapter is published (see links above); titles may be tweaked slightly over time, but the order and ideas stay the same.

Part 1: Java introduction

What is Java? (published — see link above)
How Java Works (published)
Java Setup (published)
First Java Program (published)

Part 2: Java basics

Variables in Java (published — see link above)
Data Types in Java (published)
Operators in Java (published)
Type Casting in Java (published)
User Input in Java (published)

Part 3: Control flow

if Statement (published — see link above)
if-else Statement (published)
else-if Ladder (published)
Nested if (published)
switch Statement (published)
for Loop (published)
while Loop (published)
do-while Loop (published)
break Statement (published)
continue Statement (published)

Part 4: Arrays and strings

Arrays in Java (published — see link above)
One Dimensional Array (published)
Two Dimensional Array (published)
String in Java (published)
String Methods (published)
StringBuilder (published)
StringBuffer (published)
String vs StringBuilder vs StringBuffer (published)

Part 5: Methods

Methods in Java (published — see link above)
Method Parameters (published)
Return Type (published)
Method Overloading (published)
Recursion (published)

Part 6: Object-oriented programming

Class and Object (published — see link above)
Constructor (published)
this Keyword (published)
static Keyword (published)
final Keyword (published)
Encapsulation (published)
Inheritance (published)
Polymorphism (published)
Method Overriding (published)
Abstraction (published)
Abstract Class (published)
Interface (published)
Abstract Class vs Interface (published)
Access Modifiers (published)

Part 7: Exception handling

What is Exception? (published)
try-catch (published)
finally Block (published)
throw Keyword (published)
throws Keyword (published)
Checked vs Unchecked Exception (published)
Custom Exception (published)

Part 8: Collections framework

What is Collection Framework? (published)
List Interface (published)
ArrayList (published)
LinkedList (published)
ArrayList vs LinkedList (published)
Set Interface (published)
HashSet (published)
LinkedHashSet (published)
TreeSet (published)
Map Interface (published)
HashMap (published)
REST API with PostgreSQL (Core Java) (published)
LinkedHashMap (published)
TreeMap (published)
Queue (published)
PriorityQueue (published)
Iterator (published)
Comparable and Comparator (published)

Part 9: Generics

What are Generics? (published)
Generic Class (published)
Generic Method (published)
Bounded Type Parameter (published)

Part 10: Java 8 and modern Java

Lambda Expression (published)
Functional Interface (published)
Predicate (published)
Function (published)
Consumer (published)
Supplier (published)
Stream API (published)
filter (published)
map (published)
collect (published)
reduce (published)
Optional (published)
Method Reference (published)
Date and Time API (published)

Part 11: File handling

File Handling Introduction (published)
Reading File (published)
Writing File (published)
BufferedReader (published)
Files Class (published)
Try-with-resources (published)

Part 12: Multithreading

What is Thread? (published)
Thread Class (published)
Runnable Interface (published)
Thread Lifecycle (published)
synchronized Keyword (published)
volatile Keyword (published)
ExecutorService (published)
Callable and Future (published)
CompletableFuture (published)

Part 13: JDBC and database

What is JDBC? (published)
JDBC Driver (published)
Connection (published)
PreparedStatement (published)
ResultSet (published)
CRUD with JDBC (published)
SQL Injection Prevention (published)

Part 14: APIs with Java

What is API? (published)
REST API (published)
HTTP Methods (published)
HTTP Status Codes (published)
JSON Request and Response (published)
Building API with Java (published)

Part 15: Spring Boot

What is Spring Boot? (published)
Spring Boot Project Structure (published)
Controller Layer (published)
Service Layer (published)
Repository Layer (published)
Entity (published)
DTO (published)
Dependency Injection (published)
Request Validation (published)
Global Exception Handling (published)
REST API CRUD Example (published)

Part 16: Advanced Java

Reflection (published)
Serialization (published)
Records (published)
Sealed Classes (published)
Java Modules (published)
ClassLoader (published)
JVM Memory Management (published)
Garbage Collection (published)

Part 17: Security and production

Authentication vs Authorization (published)
JWT Basics (published)
Password Hashing (published)
Input Validation (published)
CORS (published)
Logging (published)
API Versioning (published)
Pagination (published)
Rate Limiting (published)
Swagger/OpenAPI (published)
Testing with JUnit (published)
Mockito (published)
Clean Code in Java (published)
Production-Level Java Project Structure (published)
Java Roadmap and Practice Projects (published)

How to study this series

Read in order for your first pass. On the second pass, jump only to chapters where your job or project needs depth.

Always type the code yourself. Copy-paste hides typos you would have made—and those typos teach you how the compiler talks back.