What is SDKMAN?

SDKMAN! (Software Development Kit Manager) is a tool for managing parallel versions of multiple Software Development Kits on most Unix-based systems. It provides a convenient Command Line Interface (CLI) and API for installing, switching, removing and listing candidates.

SDKMAN supports various JVM-based technologies including:

• Java (Oracle JDK, OpenJDK, Amazon Corretto, GraalVM, etc.)
• Gradle - Build automation tool
• Maven - Project management tool
• Kotlin - JVM programming language
• Scala - Functional programming language
• Spring Boot CLI - Spring Boot command line interface
• And many more!

Why Use SDKMAN?

🔄 Version Management Made Easy

Switch between different Java versions with a single command - perfect for projects requiring different JDK versions.

🚀 Simple Installation Process

No need to manually download, extract, and configure environment variables. SDKMAN handles everything.

🌍 Cross-Platform Support

Works on Linux, macOS, and Windows (via WSL or Git Bash).

📦 Multiple Vendors Support

Choose from various Java distributions like Oracle JDK, OpenJDK, Amazon Corretto, AdoptOpenJDK, and more.

Prerequisites

Before installing SDKMAN, ensure your system meets these requirements:

For SDKMAN Installation:

• Unix-based system (Linux, macOS, or Windows with WSL/Git Bash)
• curl or wget installed
• bash shell (version 3.2+)

For Installing Java/SDKs (after SDKMAN is installed):

• zip and unzip utilities (needed to extract downloaded SDK archives)

You can verify these prerequisites by running:

# Check if curl is installed (required for SDKMAN installation)
curl --version

# Check bash version (required for SDKMAN)
bash --version

# Check if zip/unzip are available (needed later for SDK installations)
zip --version
unzip --version

Installing SDKMAN

Step 1: Install SDKMAN

Open your terminal and run the following command to install SDKMAN:

curl -s "https://get.sdkman.io" | bash

This command will:

• Download the SDKMAN installation script
• Install SDKMAN in your home directory (~/.sdkman)
• Add necessary configurations to your shell profile

Step 2: Initialize SDKMAN

After installation, you need to initialize SDKMAN in your current terminal session:

source "$HOME/.sdkman/bin/sdkman-init.sh"

Alternatively, you can open a new terminal window, and SDKMAN will be automatically initialized.

Step 3: Verify Installation

Confirm that SDKMAN is properly installed by checking its version:

sdk version

You should see output similar to:

SDKMAN!
script: 5.18.0
native: 0.4.6

Installing Java with SDKMAN

Now that SDKMAN is installed, let's explore how to install and manage Java versions.

List Available Java Versions

To see all available Java versions, use:

sdk list java

This will display a comprehensive list of available Java distributions and versions:

================================================================================
Available Java Versions for Linux 64bit
================================================================================
 Vendor        | Use | Version      | Dist    | Status     | Identifier
--------------------------------------------------------------------------------
 Corretto      |     | 21.0.1       | amzn    |            | 21.0.1-amzn
               |     | 17.0.9       | amzn    |            | 17.0.9-amzn
               |     | 11.0.21      | amzn    |            | 11.0.21-amzn
               |     | 8.0.392      | amzn    |            | 8.0.392-amzn
 Graal CE      |     | 21.0.1       | graalce |            | 21.0.1-graalce
               |     | 17.0.9       | graalce |            | 17.0.9-graalce
 OpenJDK       |     | 21.0.1       | open    |            | 21.0.1-open
               |     | 17.0.9       | open    |            | 17.0.9-open
               |     | 11.0.21      | open    |            | 11.0.21-open
               |     | 8.0.392      | open    |            | 8.0.392-open
 Oracle        |     | 21.0.1       | oracle  |            | 21.0.1-oracle
               |     | 17.0.9       | oracle  |            | 17.0.9-oracle
================================================================================

Install a Java Version

To install a specific Java version, use the install command with the identifier:

# Install the latest LTS version (Java 21)
sdk install java 21.0.1-open

# Install Java 17 (Previous LTS)
sdk install java 17.0.9-open

# Install Java 11 (Another LTS version)
sdk install java 11.0.21-open

# Install Amazon Corretto 17
sdk install java 17.0.9-amzn

During installation, SDKMAN will ask if you want to set this version as the default. Type Y for yes or N for no.

Install Latest Java Version

To install the latest available Java version without specifying the exact version number:

sdk install java

This will install the latest stable release and set it as your default Java version.

Managing Java Versions

Switch Between Java Versions

Use a Specific Version for Current Session

sdk use java 17.0.9-open

This switches to Java 17 for the current terminal session only.

Set Default Java Version

sdk default java 21.0.1-open

This sets Java 21 as the default version for all new terminal sessions.

List Installed Java Versions

To see all Java versions installed on your system:

sdk list java | grep installed

Or use:

sdk current java

This shows the currently active Java version.

Verify Java Installation

After installing or switching Java versions, verify the installation:

java -version
javac -version
echo $JAVA_HOME

You should see output indicating the correct Java version and JAVA_HOME path.

Additionally, you can manual setup your JAVA_HOME on .bash_profile or .zshrc:

export JAVA_HOME=${SDKMAN_CANDIDATES_DIR}/java/${CURRENT}

Advanced SDKMAN Features

Environment Configuration

SDKMAN automatically sets the JAVA_HOME environment variable when you switch Java versions. You can verify this:

echo $JAVA_HOME
# Output: /Users/username/.sdkman/candidates/java/current

Uninstall Java Versions

To remove a Java version you no longer need:

sdk uninstall java 11.0.21-open

Update SDKMAN

Keep SDKMAN up to date with:

sdk update

Flush Archives and Temp Files

Clean up downloaded archives and temporary files:

sdk flush archives
sdk flush temp

Project-Specific Java Versions

Using .sdkmanrc File

You can create a .sdkmanrc file in your project root to specify the Java version for that project:

# Navigate to your project directory
cd /path/to/your/project

# Create .sdkmanrc file
echo "java=17.0.9-open" > .sdkmanrc

# Enable auto-switching (one-time setup)
sdk config
# Set sdkman_auto_env=true

Now, whenever you cd into the project directory, SDKMAN will automatically switch to the specified Java version.

Troubleshooting Common Issues

Issue 1: Command Not Found

If you get "sdk: command not found" error:

# Check if SDKMAN is properly sourced
echo $SDKMAN_DIR

# If empty, manually source SDKMAN
source "$HOME/.sdkman/bin/sdkman-init.sh"

# Add to your shell profile permanently
echo 'source "$HOME/.sdkman/bin/sdkman-init.sh"' >> ~/.bashrc
# or for zsh users
echo 'source "$HOME/.sdkman/bin/sdkman-init.sh"' >> ~/.zshrc

Issue 2: Permission Denied

If you encounter permission issues:

# Check SDKMAN directory permissions
ls -la ~/.sdkman

# Fix permissions if needed
chmod -R 755 ~/.sdkman

Issue 3: Network Issues

If downloads fail due to network issues:

# Set proxy if needed
export http_proxy=http://your-proxy:port
export https_proxy=https://your-proxy:port

# Or configure SDKMAN with different mirror
sdk config

Best Practices

1. Keep LTS Versions

Install and maintain Long Term Support (LTS) versions for stability:

• Java 8 (LTS until 2030)
• Java 11 (LTS until 2026)
• Java 17 (LTS until 2029)
• Java 21 (LTS until 2031)

2. Use Project-Specific Versions

Create .sdkmanrc files for projects to ensure team consistency:

# Example .sdkmanrc for a Spring Boot project
java=17.0.9-open
gradle=8.4
maven=3.9.5

3. Regular Updates

Keep your Java installations updated:

# Update SDKMAN itself
sdk update

# Check for newer versions
sdk list java

# Upgrade to newer patch versions
sdk install java 21.0.2-open
sdk default java 21.0.2-open
sdk uninstall java 21.0.1-open

4. Clean Up Regularly

Remove unused versions to save disk space:

# List installed versions
sdk list java | grep installed

# Remove old versions
sdk uninstall java 8.0.382-open

# Clean up archives
sdk flush archives

Conclusion

SDKMAN is an indispensable tool for Java developers who work with multiple Java versions or JVM-based technologies. It simplifies the installation, management, and switching between different Java distributions and versions.

Key benefits of using SDKMAN:

• ✅ Effortless version management - Switch between Java versions with a single command
• ✅ Multiple vendor support - Choose from Oracle, OpenJDK, Amazon Corretto, and more
• ✅ Project-specific configurations - Use .sdkmanrc for team consistency
• ✅ Automatic environment setup - No manual JAVA_HOME configuration needed
• ✅ Cross-platform compatibility - Works on Linux, macOS, and Windows (WSL)

Whether you're maintaining legacy applications on Java 8, developing modern microservices with Java 17, or experimenting with the latest Java 21 features, SDKMAN makes it seamless to manage your Java development environment.

Start using SDKMAN today and experience the convenience of effortless Java version management!

References

• SDKMAN Official Website
• SDKMAN GitHub Repository
• Java Release Notes
• OpenJDK Website