Chapter 2 — Environment Setup

Online Java Compilers & IDEs

Quick options to write and run Java without installing anything:

• JDoodle — Simple online compile & run: JDoodle
• Repl.it — Collaborative and persistent editor: Replit
• OnlineGDB — Online debugger & editor supporting Java: OnlineGDB
• Ideone — Quick run: Ideone

Notes: Online tools are great for quick testing, learning and sharing code. They are not recommended for building production apps, working with complex dependencies, or learning tooling like Maven/Gradle.

Sample — Quick Hello World

public class HelloWorld {
    public static void main(String[] args) {
        System.out.println("Hello from online Java!");
    }
}

Local Environment Setup (Windows)

For local development on Windows, install a JDK (Java Development Kit) and configure your PATH.

1) Install a JDK

Recommended: Temurin (Eclipse Adoptium) or OpenJDK builds. Download from:

• Eclipse Adoptium (Temurin)
• OpenJDK
• Oracle JDK (requires license awareness)

2) Set JAVA_HOME and PATH (PowerShell)

1. Install JDK (example default install path: C:\Program Files\Eclipse Adoptium\jdk-17.0.7.7-hotspot).
2. Open PowerShell as Administrator and set environment variables (temporary for session):

$env:JAVA_HOME = 'C:\Program Files\Eclipse Adoptium\jdk-17.0.7.7-hotspot'
$env:PATH = $env:JAVA_HOME + '\\bin;' + $env:PATH
javac -version
java -version

To make variables permanent, use System Properties or set in the registry via System -> Advanced -> Environment Variables.

3) Compile & Run

Open a terminal (PowerShell) in the directory where you saved your local example file (e.g., HelloWorld.java) and execute:

javac HelloWorld.java
java HelloWorld

If you see version numbers, your JDK is installed correctly. If not, re-check PATH and JAVA_HOME.

Popular Java Editors & IDEs

Pick according to your goals — quick editing vs enterprise development:

• IntelliJ IDEA — Best productivity, deep Java support. Community Edition is free and great for most learners and developers.
• Eclipse — Extensible and widely used, great for large enterprise codebases.
• Visual Studio Code — Lightweight. Install the Java Extension Pack for debugging, Maven/Gradle, and code navigation.
• NetBeans — Full-featured, good for beginners and educational projects.

Tooling Tips

• Use an IDE for Java when working with multiple files, debugging, or build tools (Maven/Gradle).
• VS Code + Java Extension Pack is great for smaller or scripting-style workflows.