Java
Curriculum
Java · Backend

Java Tutorial

A complete Java path covering language basics, OOP, collections, modern Java features, testing, concurrency, and backend-ready capstones.

65 lessonsBeginner → ProBackend
Start from the beginning

Curriculum

Work through each section in order. Every lesson ends with practice and key points so the idea sticks.

Beginner

Getting Started

3 lessons · ~33 min
  1. 1
    Welcome to Java

    Why Java remains a top language for backends and Android foundations.

  2. 2
    Install the JDK

    Install a modern JDK and verify javac/java.

  3. 3
    Your First Java Program

    Compile and run a class with a main method.

Beginner

Language Basics

3 lessons · ~33 min
  1. 4
    Variables & Types

    Primitives vs reference types.

  2. 5
    Operators

    Arithmetic, relational, and logical operators.

  3. 6
    Strings

    Immutable strings, concatenation, and useful methods.

Beginner

Control Flow

2 lessons · ~22 min
  1. 7
    Conditionals

    if/else and switch expressions.

  2. 8
    Loops

    for, while, enhanced for.

Beginner

Methods

2 lessons · ~22 min
  1. 9
    Methods

    Static and instance methods with return types.

  2. 10
    Method Overloading

    Same name, different parameter lists.

Beginner

Collections Basics

3 lessons · ~33 min
  1. 11
    Arrays

    Fixed-length arrays and iteration.

  2. 12
    ArrayList

    Resizable lists from java.util.

  3. 13
    HashMap

    Key-value storage for lookups.

Beginner

OOP Foundations

5 lessons · ~55 min
  1. 14
    Classes & Objects

    Fields, constructors, and methods.

  2. 15
    Encapsulation

    private fields with getters/setters.

  3. 16
    Inheritance

    extends and method overriding.

  4. 17
    Polymorphism

    Program to interfaces and base types.

  5. 18
    Interfaces

    Contracts that classes implement.

Beginner

Projects

4 lessons · ~51 min
  1. 19
    Packages

    Organize code with package declarations.

  2. 20
    Access Modifiers

    public, private, protected, and package-private.

  3. 21
    static Members

    When state belongs to the class.

  4. 25
    Project: Quiz App

    Build a console quiz with ArrayList of questions.

Beginner

Errors

1 lessons · ~11 min
  1. 22
    Exceptions Intro

    Checked vs unchecked exceptions.

Beginner

I/O Basics

2 lessons · ~22 min
  1. 23
    Scanner Input

    Read console input safely.

  2. 24
    Reading Files

    NIO Path and Files helpers.

Intermediate

Solid OOP

1 lessons · ~13 min
  1. 26
    equals & hashCode

    Correct equality for map keys and sets.

Intermediate

Modern Java

6 lessons · ~78 min
  1. 27
    Records

    Compact immutable data carriers.

  2. 28
    Enums

    Typed constants with behavior.

  3. 29
    Generics

    Type-safe collections and methods.

  4. 30
    Streams API

    map/filter/reduce style processing.

  5. 31
    Optional

    Avoid null proliferation with Optional.

  6. 32
    Lambdas & Functional Interfaces

    Pass behavior as data.

Intermediate

Collections Advanced

2 lessons · ~26 min
  1. 33
    Collections Deep Dive

    List, Set, Map trade-offs.

  2. 34
    Sorting & Comparators

    Comparable vs Comparator.

Intermediate

Reliability

2 lessons · ~26 min
  1. 35
    Custom Exceptions

    Create domain-specific exception types.

  2. 36
    Logging Basics

    Replace System.out with structured logs.

Intermediate

Testing

1 lessons · ~13 min
  1. 37
    JUnit Testing

    Write and run unit tests.

Intermediate

Build Tools

2 lessons · ~26 min
  1. 38
    Maven Intro

    pom.xml, dependencies, and phases.

  2. 39
    Gradle Intro

    Groovy/Kotlin DSL build scripts.

Intermediate

Data Access

1 lessons · ~13 min
  1. 40
    JDBC Intro

    Connect to a database from Java.

Intermediate

Networking

2 lessons · ~26 min
  1. 41
    HTTP Client

    Call APIs with java.net.http.

  2. 42
    JSON in Java

    Parse and produce JSON with a library.

Intermediate

Concurrency

2 lessons · ~26 min
  1. 43
    Threads Basics

    Runnable, Thread, and executors overview.

  2. 44
    ExecutorService

    Thread pools for concurrent tasks.

Intermediate

Capstone Labs

2 lessons · ~38 min
  1. 45
    Project: Library Manager

    CRUD books with classes and ArrayList persistence.

  2. 46
    Project: API Client CLI

    Fetch JSON and display results.

Intermediate

Toward Backend Java

2 lessons · ~26 min
  1. 47
    Spring Boot Preview

    What Spring Boot adds for web APIs.

  2. 48
    A Tiny REST Controller

    Map HTTP endpoints conceptually with Spring.

Advanced

JVM Internals

4 lessons · ~64 min
  1. 49
    JVM Memory Model Basics

    Heap, stack, GC at a practical level.

  2. 50
    Garbage Collection Overview

    Why GC pauses matter and how to observe them.

  3. 57
    Reflection Intro

    Inspect types at runtime carefully.

  4. 58
    Java Platform Module System

    module-info.java and strong encapsulation overview.

Advanced

Performance

1 lessons · ~16 min
  1. 51
    Java Performance Tips

    Allocation pressure, streams vs loops, profiling.

Advanced

Production

2 lessons · ~32 min
  1. 52
    Security Basics

    Input validation, secrets, and dependency hygiene.

  2. 53
    Dockerize a Java App

    Containerize a JAR for deployment.

Advanced

Design

2 lessons · ~32 min
  1. 54
    GoF Patterns in Java

    Singleton, Factory, Strategy with modern taste.

  2. 55
    Clean Architecture Sketch

    Separate domain from frameworks.

Advanced

Modern Java

1 lessons · ~16 min
  1. 56
    Annotations

    Built-in and custom annotations for metadata.

Advanced

Toward Backend Java

1 lessons · ~16 min
  1. 59
    Reactive Preview

    When reactive streams help high-concurrency I/O.

Advanced

Capstone

4 lessons · ~76 min
  1. 60
    Capstone: Todo API

    In-memory REST-style service with tests.

  2. 61
    Capstone: Bank Account Domain

    Model accounts, transfers, and invariants.

  3. 62
    Capstone: CLI Toolkit

    Multi-command console tool with subcommands and tests.

  4. 63
    Capstone: File Indexer

    Walk a directory, index words, and answer queries.

Advanced

Polish & Next Steps

2 lessons · ~32 min
  1. 64
    Java Interview Review

    OOP, collections, concurrency, and JVM checklist.

  2. 65
    Next Steps in Java

    Spring, Android Kotlin path, or data engineering.