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Getting Started with Java

Welcome to the first lesson of the InnoMarts Java course. ☕

Before we start writing real Java programs, we need to prepare the tools that will help us write, compile, run, and debug Java code.

By the end of this lesson, you will have:

No complicated programming yet.

Today we are preparing the workshop before we start building things.

Getting Started with Java 25 LTS and IntelliJ IDEA

What Do We Need to Program in Java?

To develop Java applications, we need two main tools:

  1. JDK — Java Development Kit
  2. IDE — Integrated Development Environment

For this course, we will use:

Let's see what each one does.

☕ What Is the JDK?

The JDK, or Java Development Kit, contains the tools needed to develop Java applications.

It includes:

In simple terms:

The JDK gives your computer the tools needed to understand and run Java programs.

Without a JDK, you can write Java code...

but your computer will mostly stare at it politely. 😄

JDK, JVM, and JRE

You will see these abbreviations many times while learning Java.

Don't worry about memorizing every detail now.

For the moment, this is enough.

JDK

Java Development Kit

Used to develop Java applications.

It includes the Java compiler and other development tools.

JVM

Java Virtual Machine

Runs compiled Java programs.

JRE

Java Runtime Environment

Traditionally, the JRE provided the environment required to run Java applications.

For this course, we will install the complete JDK, because we want to develop Java programs, not only run them.

A simplified Java workflow looks like this:

Java source code
        ↓
     Compiler
        ↓
     Bytecode
        ↓
       JVM
        ↓
 Program running

We will explore this process properly in Lesson 3.

For now, remember:

We install the JDK because we want to write and develop Java applications.

🔎 Check Whether Java Is Already Installed

Before installing anything, open a terminal.

Run:

java --version

Then check whether the Java compiler is available:

javac --version

If Java 25 is installed, you should see output containing something similar to:

openjdk 25

and:

javac 25

Your exact version may contain additional numbers, for example:

25.0.2

That's perfectly normal.

If your terminal says that the command does not exist, Java probably needs to be installed.

🐧 Installing Java on Arch Linux

If you're using Arch Linux, installation is straightforward.

First, update the system:

sudo pacman -Syu

Then install Java 25:

sudo pacman -S jdk25-openjdk

After installation, verify Java:

java --version

Then check the compiler:

javac --version

If both commands show Java 25, your JDK is ready.

Managing Multiple Java Versions on Arch Linux

You can have several Java versions installed at the same time.

For example:

Java 21
Java 25

Arch Linux provides a convenient tool for managing them.

Run:

archlinux-java status

You may see something similar to:

Available Java environments:
  java-21-openjdk
  java-25-openjdk (default)

If Java 25 is installed but another version is selected, run:

sudo archlinux-java set java-25-openjdk

Check again:

archlinux-java status

And finally:

java --version

If Java 25 is displayed, everything is ready.

🪟 Installing Java on Windows

On Windows, install a Java 25 JDK from a trusted Java distribution.

Common choices include:

Download the installer for your system and complete the installation.

Afterward, open:

PowerShell

or:

Command Prompt

Run:

java --version

Then:

javac --version

If both commands display Java 25, the installation works.

If Windows Cannot Find Java

You may see an error similar to:

'java' is not recognized as an internal or external command

This usually means Windows cannot find the Java installation.

The JDK's bin directory needs to be available through the system PATH.

A typical Java installation might be located at:

C:\Program Files\Java\jdk-25\bin

Your exact path may be different.

Many modern JDK installers configure this automatically.

🍎 Installing Java on macOS

On macOS, install a Java 25 JDK from a trusted Java distribution.

After installation, open Terminal.

Run:

java --version

Then:

javac --version

You can also ask macOS which Java installations it knows about:

/usr/libexec/java_home -V

If Java 25 appears in the list, you're ready.

💡 IntelliJ IDEA Can Download the JDK for You

There is another convenient option.

When creating a Java project, IntelliJ IDEA can often download and configure the JDK automatically.

You may see:

Download JDK

Choose:

Java 25

and let IntelliJ configure it.

This can be especially convenient for beginners on Windows and macOS.

On Linux, especially Arch Linux, installing Java through the system package manager is often a cleaner approach because the operating system manages the Java installation directly.

🧠 What Is an IDE?

An IDE, or Integrated Development Environment, is an application designed to help developers write software.

Technically, you could write Java using:

Nano
Vim
Notepad

But an IDE gives you many useful tools in one place.

For example:

For this course, we will use IntelliJ IDEA.

💻 Why IntelliJ IDEA?

IntelliJ IDEA is very well suited to Java development.

It understands Java code and helps detect many mistakes while you type.

Throughout this course, we will use IntelliJ IDEA for:

The core Java development functionality is available without buying a paid subscription, so it is a good choice for beginners as well.

📥 Installing IntelliJ IDEA

Download IntelliJ IDEA from the official JetBrains website.

Choose your operating system:

Windows
macOS
Linux

Install it normally.

During the first launch, IntelliJ may ask you about:

For now, the default settings are perfectly fine.

We can customize everything later.

🐧 IntelliJ IDEA on Arch Linux

On Arch Linux, you have several ways to install IntelliJ IDEA.

If IntelliJ IDEA is already installed, there is no reason to reinstall it.

The important thing is simply that the IDE starts correctly and can create Java projects.

🏗 Creating Your First Java Project

Open IntelliJ IDEA.

From the welcome screen, select:

New Project

Choose:

Java

You should see a field for the JDK.

Choose:

Java 25

If Java 25 does not appear, IntelliJ may offer:

Add JDK

or:

Download JDK

Choose your Java 25 installation.

Choose a Project Name

Let's call our project:

java-course

On Linux or macOS, you might store it somewhere such as:

~/Projects/java-course

On Windows:

C:\Users\YourName\Projects\java-course

The exact location is not important.

The important thing is that you know where your project lives.

📁 Understanding the Project Structure

After creating the project, IntelliJ IDEA opens its main window.

Depending on your IntelliJ version and project configuration, you may see something similar to:

java-course
├── .idea
└── src

For now, the most important directory is:

src

src means:

source

This is where our Java source code will live.

The .idea directory contains IntelliJ IDEA project settings.

Normally, you do not need to edit those files manually.

✅ Check the Project JDK

Before continuing, make sure IntelliJ is actually using Java 25.

Open the project settings and look for:

Project SDK

or:

Project JDK

It should display something similar to:

Java 25

or:

OpenJDK 25

If so, everything is configured correctly.

🧪 Verify Your Development Environment

Let's make sure everything is ready.

Your terminal should successfully run:

java --version

and:

javac --version

IntelliJ IDEA should also show Java 25 as the project's JDK.

So our checklist now looks like this:

[✓] Java 25 installed
[✓] javac available
[✓] IntelliJ IDEA installed
[✓] Java 25 configured in IntelliJ
[✓] Java project created

If all five are true, you're ready to start programming.

🎯 Small Challenge

Before moving to Lesson 2, explore IntelliJ IDEA and find:

  1. The Project panel.
  2. The src directory.
  3. The configured JDK.
  4. The built-in terminal.
  5. The Settings or Preferences window.

You don't need to change anything.

Just look around.

Developers learn a surprising amount by pressing buttons and seeing what happens.

Preferably not the button named:

Delete Project

😄

⚠️ Common Problems

java: command not found

Java is either not installed or your terminal cannot find it.

On Arch Linux, check:

archlinux-java status

javac: command not found

You may have installed only a Java runtime instead of the full development kit.

Make sure you installed a JDK.

IntelliJ Cannot Find Java

Open your project settings and manually select the installed JDK.

Alternatively, use IntelliJ's:

Download JDK

option.

IntelliJ Uses the Wrong Java Version

You may have several Java versions installed:

Java 17
Java 21
Java 25

That is completely normal.

The operating system's default Java version and IntelliJ's project JDK can even be different.

For this course, make sure the project itself uses:

Java 25

🎓 What You Learned

In this lesson, you learned:

Your computer is now ready for Java development.

But we still haven't really programmed anything.

That changes next. ☕

Next Lesson

In Lesson 2, we will create our first Java class and finally write:

public class Main {

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

}

But we won't just copy it.

We'll begin understanding what all those mysterious words actually mean.

Continue → Lesson 2: Your First Java Program