Ja

Java

intermediate

Write once, run anywhere. Debug everywhere.

Java is a verbose, strictly typed, object-oriented language that powers Android, enterprise backends, and countless financial systems. It's been reliably annoying developers since 1995. That longevity means a massive ecosystem and rock-solid tooling.

Android DevelopmentEnterprise BackendsBig Data (Hadoop, Spark)Financial Systems
0%
0/9 lessons

Setup

Java requires the JDK (Java Development Kit). Install JDK 21 (the current LTS) and you're good to go.

Bash
# Option 1: Adoptium (Eclipse Temurin — recommended open source)
# Download the .msi from adoptium.net — check "Set JAVA_HOME" option

# Option 2: winget
winget install EclipseAdoptium.Temurin.21.JDK

# Option 3: Oracle JDK from oracle.com

# Verify (in new terminal):
java --version
javac --version

Lessons

1
Hello, World!
The famous Java Hello World. Note: it requires a class. And the class name must …
→
2
Variables & Types
Java is strictly typed. You cannot assign an int to a String. You cannot even as…
→
3
Control Flow
Java control flow is straight C-family. No surprises, no weird tricks. The enhan…
→
4
Methods
In Java, functions are called methods and must live inside classes. A small indi…
→
5
Arrays & Collections
Java arrays are fixed-size. For anything dynamic, use the Collections framework …
→
6
Classes & OOP
Java is fully committed to OOP. Everything is a class. Even the Hello World prog…
→
7
Exception Handling
Java has checked exceptions, which force you to handle or declare errors. This i…
→
8
Mini Project: Simple Bank
A console banking application that puts together classes, collections, exception…
→
9
Java Cheatsheet
Modern Java (17+) on one page — records, streams, collections.
→