How to Install Java (JDK) on Windows, macOS and Linux

Before you can write your first program, you need to install Java on your computer. To be precise, you need to install a JDK, the Java Development Kit. It takes about five minutes, and this lesson walks you through every step on Windows, macOS and Linux. At the end, you'll check that everything works, choose an editor, and run a real Java program.

What is a JDK?

The JDK (Java Development Kit) is the software package you install to write and run Java programs. It includes:

• javac: the Java compiler, which turns your .java files into bytecode.
• java: the launcher, which starts the Java Virtual Machine (JVM) and runs your program.
• The standard library: thousands of ready-made classes for text, math, files, dates, lists and much more.
• Extra tools such as jshell (an interactive Java console) and javadoc (a documentation generator).

You may also see the term JRE (Java Runtime Environment). A JRE can only run Java programs; it has no compiler. As a programmer, you always want the JDK. You'll see exactly how the JDK, JRE and JVM relate in How Java Works.

Which Java version should you install?

Java gets a new version every six months, and every two years one of them is an LTS (long-term support) release that receives updates for many years. We recommend Java 21, an LTS release, or any newer LTS such as Java 25. Every example in this course runs on Java 17 or newer, so if your school or job already has Java 17 installed, you're fine.

Where to download the JDK

Java is open source, so several companies publish free builds of the same JDK. They all behave the same for learning. Two popular choices:

Other builds, such as Amazon Corretto, Microsoft Build of OpenJDK or Azul Zulu, work just as well.

How to install Java on Windows

Option 1: with winget (the package manager built into Windows 10 and 11). Open PowerShell or Windows Terminal and run:

winget install EclipseAdoptium.Temurin.21.JDK

Option 2: with the installer. Go to adoptium.net, download the .msi installer for Windows x64, and run it. On the "Custom Setup" screen, make sure Add to PATH is turned on, and also turn on Set JAVA_HOME variable. Then click through to finish.

Either way, close your terminal and open a new one afterwards. A terminal only picks up new programs when it starts.

How to install Java on macOS

Option 1: with Homebrew (a popular package manager for macOS). In the Terminal app, run:

brew install --cask temurin@21

Option 2: with the installer. Download the .pkg file from adoptium.net. Pick aarch64 for Macs with Apple chips (M1, M2 and later) or x64 for older Intel Macs. Open it and follow the steps.

How to install Java on Linux

Most Linux distributions offer OpenJDK in their package manager. On Ubuntu or Debian:

sudo apt update
sudo apt install openjdk-21-jdk

If your distribution doesn't have version 21 yet, install openjdk-17-jdk instead; it works for this course. On Fedora:

sudo dnf install java-21-openjdk-devel

Make sure the package name ends in -jdk or -devel. Packages without it may install only the runtime, without the compiler.

How to check that Java is installed

Open a new terminal and run these two commands:

java -version
javac -version

The first command prints two or three lines about your Java runtime. The first line contains the version number, for example something like openjdk version "21.0.5"; the exact numbers and the vendor name depend on what you installed. The second command prints one short line, such as javac 21.0.5. If both commands show a version of 17 or higher, you're ready to go.

Choosing an editor or IDE

You can write Java in any plain text editor, but a good tool colors your code, spots typos as you type, and runs programs with one click. An IDE (integrated development environment) bundles all of that.

How to run your first Java program

Let's prove the setup works. Create a folder, for example java-course, and inside it a file named exactly Hello.java with this code:

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

Hello from Java!
Your setup works.

Open a terminal in that folder (or use cd java-course to move into it). There are two ways to run the program.

Way 1: run the source file directly

java Hello.java

Since Java 11, the java command can take a single .java file, compile it in memory, and run it straight away. No extra files are created. This is the quickest way to try small programs, and it's how every example in this course can be run.

Way 2: compile with javac, then run with java

javac Hello.java
java Hello

The first command compiles your code and creates a new file, Hello.class, containing bytecode. The second command runs that compiled class. Notice that you type java Hello, the class name, without .java or .class on the end. This two-step way is what real projects use, because you compile once and run many times.

Both ways print the same two lines you saw above.

Common mistakes when installing Java

1. Installing a JRE instead of a JDK

If java -version works but javac -version says "not found", you have only a runtime. Install a full JDK.

2. Using an old terminal window

A terminal that was open during the installation doesn't know about Java yet. Close it and open a new one.

3. Typing java Hello.class

After compiling with javac, run the class by name: java Hello. Adding .class gives an error like Could not find or load main class Hello.class.

4. Running from the wrong folder

If Java says it can't find Hello.java, your terminal is in a different folder. Use cd to move to the folder that contains the file.

5. Several Java versions fighting

If java -version and javac -version show different numbers, an older Java is earlier on your PATH. Remove the old one or put the new JDK's bin folder first.

Practice exercise

public class SetupCheck {
    public static void main(String[] args) {
        System.out.println("Name: Priya");
        System.out.println("Editor: IntelliJ IDEA");
        System.out.println("Ready to learn Java!");
    }
}

Name: Priya
Editor: IntelliJ IDEA
Ready to learn Java!

What's next?

Java is installed and you've already run a program. Next, take a closer look at that code and learn what every single word means in Java Hello World: Your First Program.