Initial Setup

Ever wondered how enterprise systems that process millions of transactions daily get started? It begins exactly where you are now - setting up your development environment. This tutorial provides the quickest path to running your first Java program. You’ll install the Java Development Kit (JDK), verify it works, and run a simple “Hello World” application.

What You’ll Achieve

By the end of this tutorial, you’ll have:

✅ Java Development Kit (JDK 21 or later) installed on your system
✅ Verified Java installation works correctly
✅ Created and compiled your first Java program
✅ Run your first Java application successfully

Prerequisites

Basic command line familiarity - You should know how to open a terminal/command prompt and navigate directories
No programming experience required - This tutorial assumes you’re completely new to Java

Learning Path

  graph TD
    A[Initial Setup<br/>THIS TUTORIAL] --> B[Quick Start<br/>Basic Syntax]
    B --> C[Beginner<br/>OOP Foundations]
    C --> D[Intermediate<br/>Advanced OOP]
    D --> E[Advanced<br/>Concurrency & Patterns]

    style A fill:#0173B2,stroke:#000000,color:#fff
    style B fill:#029E73,stroke:#000000,color:#fff
    style C fill:#DE8F05,stroke:#000000,color:#fff
    style D fill:#CC78BC,stroke:#000000,color:#fff
    style E fill:#CA9161,stroke:#000000,color:#fff

Why Learn Java?

Java is one of the world’s most popular programming languages, powering:

Enterprise applications - Banking systems, e-commerce platforms, large-scale business applications
Android mobile apps - The primary language for Android app development
Cloud services - Microservices, serverless functions, distributed systems
Big data systems - Hadoop, Apache Spark, Kafka, and other data processing frameworks

Java’s “write once, run anywhere” philosophy means code runs on any platform with a Java Virtual Machine (JVM).

Step 1: Install the Java Development Kit (JDK)

The JDK contains everything you need to develop Java applications: compiler, runtime, and standard libraries.

Choose Your Installation Method

We recommend OpenJDK - the free, open-source implementation of Java.

Option A: Download from Adoptium (Recommended)

Adoptium provides high-quality, free OpenJDK binaries for all platforms.

Visit https://adoptium.net/
Select “JDK 21 (LTS)” from the version dropdown
Download the installer for your operating system
Run the installer and follow the prompts

Option B: Use a Package Manager

macOS (Homebrew):

brew install openjdk@21

After installation, link it to your system:

sudo ln -sfn /opt/homebrew/opt/openjdk@21/libexec/openjdk.jdk /Library/Java/JavaVirtualMachines/openjdk-21.jdk

Linux (Ubuntu/Debian):

sudo apt update
sudo apt install openjdk-21-jdk

Linux (Fedora/RHEL):

sudo dnf install java-21-openjdk-devel

Windows (Chocolatey):

choco install openjdk21

Platform-Specific Installation Notes

Windows

The installer will typically install to C:\Program Files\Eclipse Adoptium\jdk-21.x.x\
The installer should automatically set your PATH environment variable
If not, you’ll need to manually add the bin directory to your PATH

macOS

JDK is installed to /Library/Java/JavaVirtualMachines/
The java command should be available immediately after installation
You may need to restart your terminal

Linux

Package managers handle PATH configuration automatically
JDK is typically installed to /usr/lib/jvm/
No additional configuration needed

Step 2: Verify Installation

Open a terminal (or command prompt on Windows) and run:

java -version

Expected output (version numbers may vary):

openjdk version "21.0.1" 2023-10-17 LTS
OpenJDK Runtime Environment Temurin-21.0.1+12 (build 21.0.1+12-LTS)
OpenJDK 64-Bit Server VM Temurin-21.0.1+12 (build 21.0.1+12-LTS, mixed mode, sharing)

Also verify the compiler is available:

javac -version

Expected output:

javac 21.0.1

Troubleshooting Installation

“Command not found” error?

Windows: Add JDK bin directory to PATH (e.g., C:\Program Files\Eclipse Adoptium\jdk-21.x.x\bin)
macOS/Linux: Your package manager should have configured PATH automatically. Try restarting your terminal

Wrong version displayed?

You may have multiple Java versions installed
Use which java (macOS/Linux) or where java (Windows) to see which version is active
Uninstall older versions or update your PATH to prioritize JDK 21

Permission denied?

Use sudo on Linux/macOS for installation commands
Run PowerShell/Command Prompt as Administrator on Windows

Step 3: Create Your First Java Program

Let’s write a simple “Hello World” program to verify everything works.

Create a Project Directory

mkdir hello-java
cd hello-java

Write the Code

Create a file named Hello.java with the following content:

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

Important naming rule: The filename Hello.java MUST exactly match the class name Hello (case-sensitive). This is a Java requirement.

Understanding the Code (Brief)

public class Hello - Defines a class named “Hello”
public static void main(String[] args) - The entry point where Java starts execution
System.out.println() - Prints text to the console
Every Java program must have at least one class and a main method to run

Note: You’ll learn these concepts in detail in the Quick Start and Beginner tutorials.

Step 4: Compile the Program

Compile your Java code into bytecode that the JVM can run:

javac Hello.java

If successful, this command creates a file named Hello.class (the compiled bytecode). No output means success.

Check that the file was created:

ls  # macOS/Linux
dir # Windows

You should see both Hello.java (source) and Hello.class (compiled bytecode).

Troubleshooting Compilation

“error: class Hello is public, should be declared in a file named Hello.java”

Your filename doesn’t match the class name
Make sure the file is named exactly Hello.java (case-sensitive)

“javac: command not found”

JDK is not installed or not in your PATH
Go back to Step 1 and verify installation

Syntax errors?

Make sure you copied the code exactly as shown
Check for missing semicolons, braces, or parentheses

Step 5: Run the Program

Execute your compiled program:

java Hello

Expected output:

Hello, Java!

Note: Run with java Hello (no .class extension), not java Hello.class.

How This Works

javac Hello.java - The Java compiler translates source code into bytecode
Hello.class - The bytecode file created by the compiler
java Hello - The JVM loads and executes the bytecode

This two-step process (compile → run) is fundamental to Java development.

Verification Checklist

Confirm you can do all of the following:

✅ Run java -version and see Java 21 or later
✅ Run javac -version and see the compiler version
✅ Create a .java file with a simple program
✅ Compile it with javac to produce a .class file
✅ Run it with java and see the output

If all checkboxes are checked, you’re ready to start learning Java!

🎯 Quick Challenge

Now that you have Java working, try this quick challenge to solidify your understanding:

Challenge: Modify the Hello World Program

Edit Hello.java and change the message to print your name instead of “Hello, Java!”
Compile it again with javac Hello.java
Run it with java Hello and verify your name appears

Success criteria:

Program compiles without errors
Program runs without errors
Your custom message displays

Challenge: Create a Second Program

Try creating another Java program from scratch:

Create a file named Calculator.java

Write a class with a main method that performs a simple calculation:

int x = 10;
int y = 20;
System.out.println("Sum: " + (x + y));

Compile and run it
Verify the output shows the correct sum (30)

Hint: Remember the class name must match the filename (Calculator.java for class Calculator).

These challenges confirm that your Java setup is complete and working properly.

Optional: Set Up an IDE

While you can develop Java with a text editor and command line, an Integrated Development Environment (IDE) provides code completion, debugging, and other helpful features.

Popular Java IDEs

IntelliJ IDEA Community Edition (Recommended)

Download: https://www.jetbrains.com/idea/download/
Free and feature-rich
Excellent code completion and refactoring
Built-in Maven and Gradle support

Eclipse

Download: https://www.eclipse.org/downloads/
Free and open-source
Lightweight and highly customizable
Large plugin ecosystem

Visual Studio Code

Download: https://code.visualstudio.com/
Free and lightweight
Install “Extension Pack for Java” from Microsoft
Good for beginners, less feature-rich than IntelliJ or Eclipse

You don’t need an IDE right now. For the Initial Setup and Quick Start tutorials, the command line is sufficient. IDEs become more valuable as projects grow larger.

Next Steps

Congratulations! You have a working Java development environment.

Continue Learning

Java Quick Start - Learn enough Java to explore independently. Perfect if you want a quick overview of core syntax and concepts.
Complete Beginner’s Guide to Java - Comprehensive foundation covering Java fundamentals from zero. Choose this if you want in-depth coverage with practice exercises.