Here’s a step-by-step guide to install Java 21 and set up your development environment:

Step 1: Download and Install Java 21

1. Download JDK 21:
   • Go to the official Oracle Java SE Downloads page or use Adoptium or OpenJDK for an open-source version.
   • Download the JDK 21 version suitable for your system (Windows, macOS, or Linux).
2. Install Java 21:
   • Windows:
     • Run the installer file and follow the prompts.
   • macOS:
     • Use the .dmg package and follow the installation instructions.
   • Linux:
     • Extract the .tar.gz archive or use a package manager like apt or yum if supported by your Linux distribution.
     • Example for Ubuntu/Debian:

       sudo apt update
       sudo apt install openjdk-21-jdk
       

Step 2: Set JAVA_HOME and PATH

Once Java is installed, set the JAVA_HOME and add the binary folder to your PATH.

Windows:

1. Open System Properties:
   • Press Win + S, search for “Environment Variables,” and click it.
2. Add a JAVA_HOME variable:
   • Click New under System Variables.
   • Variable Name: JAVA_HOME
   • Variable Value: Path to the JDK installation directory (e.g., C:\Program Files\Java\jdk-21).
3. Update the PATH variable:
   • Select the Path variable, click Edit, and add %JAVA_HOME%\bin.

macOS / Linux:

1. Open your terminal and edit your shell configuration file (e.g., ~/.bashrc, ~/.zshrc, or ~/.bash_profile):

   export JAVA_HOME=/path/to/java/jdk-21
   export PATH=$JAVA_HOME/bin:$PATH
   

2. Apply the changes:

   source ~/.bashrc
   # or
   source ~/.zshrc
   

3. Verify the installation:

   java -version
   

Step 3: Set Up IntelliJ IDEA

1. Download IntelliJ IDEA:
   • Visit the IntelliJ IDEA website and download the latest version.
   • Install the Ultimate Edition or the Community Edition, depending on your needs.
2. Configure IntelliJ IDEA with Java 21:
   • Open IntelliJ IDEA and go to File > Project Structure > SDKs.
   • Click + to add a new JDK.
   • Navigate to the Java 21 installation folder and select it.
3. Set the project’s JDK version:
   • Go to File > Project Structure > Modules and assign the JDK 21 to your project.

Step 4: Verify the Java Development Setup

1. Create a sample application to test the setup:
   • Create a new Java project in IntelliJ.
   • Write a “Hello, World!” program:

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

   • Run the program to ensure it works as expected.
2. Confirm the Java version:
   • Run the following in the terminal:

   java -version
   

3. IntelliJ’s terminal should point to Java 21.

Optional: Tools to Enhance Development

1. Maven/Gradle:
   • Set up Maven or Gradle build tools for dependency management.
2. Version Control:
   • Install Git and set it up in IntelliJ.
3. Extensions and Plugins:
   • Install helpful IntelliJ plugins like Lombok, Checkstyle, JRebel, or a Database tool.
4. Docker:
   • If you’re working with containers, install Docker and configure IntelliJ’s Docker plugin.

You now have Java 21 and your development environment fully set up and configured!