Download and Install Java

What Do You Need to Install?

To write and run Java programs you need the Java Development Kit (JDK). It includes:

• javac — the Java compiler that turns your source code into bytecode
• java — the JVM launcher that runs bytecode
• jar, javadoc — packaging and documentation tools
• JRE — the runtime environment (bundled inside the JDK)

LTS Version Overview

Installation Guide

• 💻 Windows
•  macOS
• 🐧 Linux

java -version
javac -version

/bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"

brew install openjdk@21

sudo ln -sfn $(brew --prefix openjdk@21)/libexec/openjdk.jdk /Library/Java/JavaVirtualMachines/openjdk-21.jdk
echo 'export JAVA_HOME=$(brew --prefix openjdk@21)' >> ~/.zshrc
source ~/.zshrc

echo 'export JAVA_HOME=$(/usr/libexec/java_home -v 21)' >> ~/.zshrc
source ~/.zshrc

java -version
javac -version

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

echo 'export JAVA_HOME=/usr/lib/jvm/java-21-openjdk-amd64' >> ~/.bashrc
echo 'export PATH=$JAVA_HOME/bin:$PATH' >> ~/.bashrc
source ~/.bashrc

sudo dnf install java-21-openjdk-devel -y

sudo pacman -S jdk21-openjdk

java -version
javac -version

Verify Your Installation

Open a terminal (or Command Prompt on Windows) and run these two commands:

java -version
javac -version

Both commands must return a version number. If you get "command not found" or "not recognized", the PATH is not set correctly — revisit Step 3 of your OS section above.

Write and Run Your First Program

Once Java is installed, confirm everything works end-to-end:

public class HelloWorld {
    public static void main(String[] args) {
        System.out.println("Java is installed and working!");
    }
}

javac HelloWorld.java

java HelloWorld

Oracle JDK vs OpenJDK

Managing Multiple Java Versions

If you need to switch between Java versions (e.g. Java 11 for an old project and Java 21 for a new one), use a version manager:

• SDKMAN (macOS / Linux) — sdk install java 21-tem then sdk use java 21-tem
• Jabba (Windows / macOS / Linux) — cross-platform JDK version manager
• Windows: manually update JAVA_HOME to point to the desired version folder

# SDKMAN example (macOS/Linux)
sdk list java          # see available versions
sdk install java 21-tem
sdk install java 17-tem
sdk use java 17-tem    # switch for current session
sdk default java 21-tem # set global default