Installing JDK and IDE for Spring Boot

Before a carpenter builds a single chair, they set up a workbench and lay out their tools. If the saw is blunt or the bench wobbles, every job after that goes badly. Your Spring Boot workbench has two parts: the JDK, which compiles and runs Java, and an IDE, the editor where you write and run your code. Set them up properly once and you will not think about them again.

This guide walks you through installing Java 21, pointing your computer at it, checking that everything works, and choosing an editor. You do not need to install Maven separately; you will see why near the end.

What is a JDK, and which one do you need?

You may also hear about the JRE and the JVM. Here is how they fit inside each other:

Spring Boot 4 needs Java 17 or newer. This course uses Java 21, a long-term support (LTS) release, which means it gets security fixes for years. Newer versions such as Java 25 also work fine.

Several companies build free JDKs from the same OpenJDK source code. Eclipse Temurin, Amazon Corretto, Microsoft Build of OpenJDK and Oracle's OpenJDK builds all behave the same for learning. If you are unsure, pick Eclipse Temurin 21 from adoptium.net.

Why do you need both a JDK and an IDE?

The JDK does the real work: it turns your .java files into bytecode and runs them. You could write code in Notepad and build it from the terminal, but an IDE (Integrated Development Environment) makes daily work much faster:

• It highlights mistakes as you type, before you even run the code.
• It completes class names, methods and imports for you.
• It understands Maven, so it downloads libraries and shows your project structure.
• It runs and debugs your Spring Boot app with one click, and lets you pause code to inspect values.

In short, the JDK is the engine and the IDE is the dashboard that makes the engine easy to drive.

How it works

Here is the full setup journey. Each step depends on the one before it.

text
Download JDK 21 installer
        |
        v
Install it
        |
        v
Set JAVA_HOME and PATH
        |
        v
Check: java -version
        |
        v
Install an IDE
        |
        v
Open a Spring Boot project
        |
        v
Run it with the IDE or mvnw

The middle step is the one people skip. JAVA_HOME tells tools like Maven and your IDE where Java lives, and PATH lets you type java in any terminal. If the check step fails, go back one step, not forward.

Installing the JDK

Windows

1. Download the Temurin 21 .msi installer for Windows x64 from adoptium.net.
2. Run it. On the feature screen, switch on "Set JAVA_HOME variable" and "Add to PATH" if they are offered.
3. Close every open terminal and open a new one, so it picks up the new settings.

If the installer did not set them, open Edit the system environment variables, click Environment Variables, add a system variable JAVA_HOME pointing to the JDK folder (for example C:\Program Files\Eclipse Adoptium\jdk-21...), then add %JAVA_HOME%\bin to Path.

macOS

Download the .pkg installer for your chip (Apple silicon or Intel) and run it, or use Homebrew with brew install --cask temurin@21. Then add this line to ~/.zshrc and open a new terminal:

bash
export JAVA_HOME=$(/usr/libexec/java_home -v 21)

Linux (Ubuntu)

bash
sudo apt update
sudo apt install openjdk-21-jdk

Most Linux tools find Java through PATH automatically. Set JAVA_HOME in ~/.bashrc if a tool asks for it.

bash
java -version
javac -version

java
public class JavaCheck {
    public static void main(String[] args) {
        String version = System.getProperty("java.version");
        int major = Runtime.version().feature();

        System.out.println("Java version: " + version);
        if (major >= 17) {
            System.out.println("Ready for Spring Boot 4");
        } else {
            System.out.println("Too old: install Java 17+");
        }
    }
}

bash
java JavaCheck.java

text
Java version: 21.0.12.1
Ready for Spring Boot 4

Choosing an IDE

Any of them works for this course. Pick one and stay with it for a while; switching editors every week slows you down more than any feature helps.

You Do Not Need to Install Maven

Every project made with Spring Initializr includes the Maven Wrapper: the mvnw script (and mvnw.cmd on Windows). The first time you run it, it downloads the right Maven version into your home folder. So inside a project you type ./mvnw spring-boot:run on macOS and Linux, or mvnw.cmd spring-boot:run on Windows, and it just works. Installing Maven yourself is optional.

Common Mistakes

• An old Java wins. If java -version shows 1.8 or 11, an older Java is earlier in your PATH. Move the Java 21 entry up, or remove the old one.
• Using an old terminal. Environment changes only reach terminals opened after the change. Close and reopen it.
• Installing only a JRE. Without the JDK there is no javac, so builds fail with "No compiler is provided".

Interview Questions

Frequently Asked Questions

Which Java version is best for Spring Boot?

Use a long-term support version: Java 21 is a safe choice for this course, and Java 25 also works. Spring Boot 4 will not run on anything older than Java 17.

Is OpenJDK free for commercial use?

Yes. OpenJDK builds such as Eclipse Temurin, Amazon Corretto and Microsoft Build of OpenJDK are free to use at work and at home.

Can I have more than one Java version installed?

Yes. Many developers keep two or three. JAVA_HOME and PATH decide which one your terminal and tools use.

Do I need an internet connection to build Spring Boot apps?

The first build downloads Maven and the libraries your project uses. After that, they are cached on your computer, so later builds work offline unless you add new libraries.

Related Topics

• Creating a Project with Spring Initializr: generate your first project now that Java is ready.
• Running a Spring Boot Application: every way to start your app.
• Maven pom.xml Explained: what Maven does with your project file.