Complete Guide

Complete Java Tutorial

Java is one of the most in-demand programming languages in the world — and for good reason. It powers Android apps, enterprise backends, and systems that handle millions of requests a day. This guide covers all 223 Java topics on TheCodeForge, from your first Hello World to advanced concurrency and Spring Boot.

Learning Roadmap

Beginner → Learn Java syntax, OOP basics and how the JVM works

Intermediate → Explore collections, streams, exception handling and design patterns

Advanced → Master concurrency, JVM internals, Spring Boot and microservices

223

Topics

59

Beginner

114

Intermediate

50

Advanced

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Java Basics (13)Control Flow (9)Arrays (8)OOP Concepts (16)Strings (15)Exception Handling (6)Collections (21)Java 8+ Features (16)Multithreading (10)Java I/O (8)Advanced Java (28)Spring Boot (21)Hibernate & JPA (7)Build Tools (5)Concurrency (6)Spring Security (4)Spring Cloud (9)Messaging (7)Microservices Patterns (3)Deployment (3)Performance (1)Production (3)Interview (4)

Java Basics

Introduction to Java Beginner JDK vs JRE vs JVM Explained Beginner Java Program Structure Beginner Data Types in Java Beginner Variables and Constants in Java Beginner Operators in Java Beginner Type Casting in Java Beginner Input and Output in Java Beginner Comments in Java Beginner Java Keywords and Identifiers Beginner Java Access Modifiers Beginner Java Wrapper Classes Beginner Autoboxing and Unboxing in Java Intermediate

Control Flow

if-else Statement in Java Beginner switch Statement in Java Beginner for Loop in Java Beginner while and do-while Loop in Java Beginner break and continue in Java Beginner Nested Loops in Java Beginner Enhanced for Loop in Java Beginner Ternary Operator in Java Beginner Labeled break and continue in Java Intermediate

Arrays

Arrays in Java Beginner Multi-dimensional Arrays in Java Intermediate Array Sorting in Java Beginner Array Searching in Java Beginner Arrays Class in Java Intermediate Jagged Arrays in Java Intermediate Copying Arrays in Java Beginner Sparse Arrays in Java Advanced

OOP Concepts

Classes and Objects in Java Beginner Constructors in Java Beginner Inheritance in Java Intermediate Polymorphism in Java Intermediate Encapsulation in Java Intermediate Abstraction in Java Intermediate Interfaces in Java Intermediate Abstract Classes in Java Intermediate Method Overloading in Java Beginner Method Overriding in Java Intermediate super and this Keywords in Java Intermediate static Keyword in Java Intermediate final Keyword in Java Intermediate Object Class in Java Intermediate instanceof Operator in Java Beginner Nested and Inner Classes in Java Intermediate

Strings

Strings in Java Beginner String Methods in Java Beginner StringBuilder and StringBuffer in Java Intermediate String Formatting in Java Beginner Regular Expressions in Java Intermediate String Comparison in Java Beginner String Immutability in Java Intermediate String Pool in Java Advanced String Tokenizer in Java Intermediate Character Class in Java Beginner Char Array to String in Java: Four Conversion Methods Beginner List to Comma Separated String in Java Beginner Java String contains(): Check for Substrings Beginner Java Split String: By Delimiter, Regex and Limit Beginner Java String replace(), replaceAll() and replaceFirst() Beginner

Exception Handling

Exception Handling in Java Intermediate try-catch-finally in Java Intermediate Custom Exceptions in Java Intermediate throws and throw in Java Intermediate Checked vs Unchecked Exceptions Intermediate Multi-catch and Finally Block Intermediate

Collections

Collections Framework Overview Intermediate ArrayList in Java Intermediate LinkedList in Java Intermediate HashMap in Java Intermediate HashSet in Java Intermediate TreeMap and TreeSet in Java Intermediate Stack and Queue in Java Intermediate Iterator and ListIterator in Java Intermediate LinkedHashMap and LinkedHashSet Intermediate PriorityQueue in Java Intermediate Comparable and Comparator in Java Intermediate Collections Utility Class in Java Intermediate Deque and ArrayDeque in Java Intermediate ConcurrentHashMap in Java Advanced EnumMap and EnumSet in Java Intermediate WeakHashMap in Java Advanced IdentityHashMap in Java Advanced Java flatMap(): Flatten Streams and Optional Intermediate HashMap vs Hashtable in Java Beginner Java Stream filter(): Filter Collections with Lambdas Beginner Java Map containsKey(): Check if a Key Exists Beginner

Java 8+ Features

Lambda Expressions in Java Intermediate Stream API in Java Intermediate Optional Class in Java Intermediate Functional Interfaces in Java Intermediate Method References in Java Intermediate Default Methods in Interface Intermediate Date and Time API in Java 8 Intermediate forEach and Map Operations in Stream Intermediate Collectors in Java Stream API Advanced var Keyword in Java 10 Beginner Records in Java 16 Intermediate Sealed Classes in Java 17 Advanced Pattern Matching in Java Advanced CompletableFuture vs Future Advanced Text Blocks in Java 15 Beginner Java 25 New Features — What Changed and Why Minecraft Upgraded Intermediate

Multithreading

Multithreading in Java Advanced Thread Lifecycle in Java Advanced Synchronization in Java Advanced Executors and Thread Pools in Java Advanced volatile Keyword in Java Advanced Deadlock in Java Advanced wait notify and notifyAll in Java Advanced CompletableFuture in Java Advanced Atomic Classes in Java Advanced CountDownLatch and CyclicBarrier Advanced

Java I/O

File Handling in Java Intermediate FileReader and FileWriter in Java Intermediate BufferedReader and BufferedWriter Intermediate Serialization in Java Advanced NIO in Java Advanced Working with JSON in Java Intermediate Java Scanner Class Beginner Java PrintWriter and PrintStream Intermediate

Advanced Java

Generics in Java Advanced Reflection API in Java Advanced Annotations in Java Intermediate Enums in Java Intermediate Inner Classes in Java Intermediate Anonymous Classes in Java Intermediate Design Patterns in Java Advanced Singleton Pattern in Java Intermediate Factory Pattern in Java Intermediate Builder Pattern in Java Intermediate Garbage Collection in Java Advanced JVM Memory Model Advanced JVM Memory Issues in Production: Debugging Guide (OOM, GC, Leaks) Intermediate JVM GC Tuning Guide: G1, ZGC, Shenandoah Explained with Real Trade-offs Intermediate Observer Pattern in Java Intermediate Strategy Pattern in Java Intermediate Decorator Pattern in Java Intermediate Dependency Injection in Java Advanced Java Modules — JPMS Advanced Java Memory Leaks and Prevention Advanced Spring Boot Introduction Intermediate Maven vs Gradle in Java Intermediate Java Profiling and Performance Advanced Java Logging with SLF4J and Logback Intermediate Java Agent and Instrumentation Advanced JUnit 5 Annotations: @Test, @BeforeEach, @AfterEach and More Beginner Mockito verify(): How to Assert Method Calls in Unit Tests Intermediate Unit Testing vs Integration Testing: Key Differences Beginner

Spring Boot

Spring Boot Application Properties Explained Beginner Spring Boot Project Structure Beginner Spring Boot Auto-Configuration Explained Beginner Building a REST API with Spring Boot Beginner Spring Boot Annotations Cheat Sheet Beginner Spring Boot with MySQL and JPA Intermediate Spring Boot Exception Handling Intermediate Spring Boot Validation with Bean Validation API Intermediate Spring Boot Security Basics Intermediate JWT Authentication with Spring Boot Intermediate Spring Boot Actuator and Monitoring Intermediate Spring Boot Testing with JUnit and Mockito Intermediate Spring Boot with Docker Advanced Microservices with Spring Boot and Spring Cloud Advanced Spring Boot Caching with Redis Advanced Spring Boot Bean Lifecycle Intermediate Autowiring in Spring Boot Intermediate Scheduling Tasks with @Scheduled Intermediate @Async and Async Processing in Spring Boot Intermediate File Upload in Spring Boot Intermediate API Documentation with Swagger/OpenAPI Intermediate

Hibernate & JPA

Introduction to Hibernate ORM Beginner Hibernate vs JPA — What's the Difference Beginner Hibernate Entity Mapping Explained Beginner One-to-Many and Many-to-Many in Hibernate Intermediate HQL vs JPQL vs Native SQL Intermediate Hibernate Caching — First and Second Level Intermediate Hibernate N+1 Problem and How to Fix It Advanced

Build Tools

Maven Tutorial for Beginners Beginner Maven vs Gradle — Which Should You Use Beginner Understanding pom.xml in Maven Beginner Maven Dependency Management Explained Intermediate Gradle Build Script Basics Beginner

Concurrency

Java Threads and Runnable Explained Intermediate Java Executor Service and Thread Pools Intermediate synchronized Keyword in Java Intermediate Java Locks and ReentrantLock Advanced Java CompletableFuture Explained Advanced Deadlock in Java — Causes and Prevention Advanced

Spring Security

Password Encoding and BCrypt in Spring Security Beginner OAuth2 with Spring Security Intermediate Refresh Token with Spring Boot JWT Intermediate Role-Based Access Control with Spring Security Intermediate

Spring Cloud

Service Discovery with Spring Cloud Eureka Intermediate API Gateway with Spring Cloud Gateway Intermediate Feign Client in Spring Boot Microservices Intermediate Circuit Breaker Pattern with Resilience4j Intermediate Resilience4j — Retry, Circuit Breaker & Rate Limiting Intermediate Centralized Config with Spring Cloud Config Intermediate Distributed Tracing with Zipkin and Micrometer Intermediate Load Balancing with Spring Cloud LoadBalancer Intermediate Inter-service Communication in Microservices Intermediate

Messaging

Apache Kafka with Spring Boot — Getting Started Intermediate Kafka Producer and Consumer in Spring Boot Intermediate RabbitMQ with Spring Boot Intermediate Dead Letter Queue in Spring Boot Intermediate Event-Driven Architecture with Spring Boot Intermediate Async Messaging Patterns in Spring Boot Intermediate Retry Mechanism in Spring Boot Intermediate

Microservices Patterns

Database-per-Service Pattern in Microservices Advanced Saga Pattern for Distributed Transactions Advanced CQRS Pattern in Spring Boot Microservices Advanced

Deployment

Spring Boot Production Deployment Guide Intermediate CI/CD for Spring Boot with GitHub Actions Intermediate Deployment Rollback Strategies for Spring Boot Advanced

Performance

High Traffic Handling in Spring Boot Advanced

Production

Spring Boot Real-world Debugging Scenarios Advanced API Timeout Handling in Spring Boot Advanced Microservices Failure Recovery Patterns Advanced

Interview

Spring Boot Interview Questions Advanced Microservices Interview Questions Advanced Spring Security Interview Questions Advanced Design Patterns Interview Questions for Java Advanced

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