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Overview

JavaOptionsCli provides a streamlined workflow for managing multiple Java installations. This guide walks through the complete process from downloading Java to switching between versions.

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Step 1: Download Java

Download the Java version you want to install as a .tar.gz archive.
Choose the Linux x64 compressed archive (.tar.gz) format. Files are typically named like jdk-21_linux-x64_bin.tar.gz or OpenJDK17U-jdk_x64_linux_hotspot_17.0.1_12.tar.gz.

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Step 2: Prepare your workspace

Place the downloaded .tar.gz file in a dedicated directory: 
mkdir ~/java-downloads
cd ~/java-downloads
mv ~/Downloads/jdk-21_linux-x64_bin.tar.gz .
JavaOptionsCli must be executed from the same directory where the .tar.gz file is located. This is a current design requirement.

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Step 3: Run JavaOptionsCli

Launch the interactive CLI from the directory containing your tar.gz file: 
JavaOptionsCli
For easier access, consider moving the binary to /usr/bin/ or creating an alias:
# Option 1: Make it globally available
sudo mv JavaOptionsCli /usr/bin/JavaOptionsCli

# Option 2: Create an alias
echo 'alias javaoptionscli="/path/to/JavaOptionsCli"' >> ~/.bashrc
source ~/.bashrc

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Step 4: Install a new Java version

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Select installation option

From the main menu, choose New Version Java.

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Provide the tar.gz filename

When prompted, enter the exact name of your tar.gz file: 
Enter the name of the tar file
jdk-21_linux-x64_bin.tar.gz

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Specify the folder name

The tool will extract the archive and show your /opt/java directory. Enter the extracted folder name: 
Enter the folder for the new Java version
jdk-21
The folder name must exactly match the extracted directory name. Common examples: jdk-21, jdk-17.0.1, jdk-11.0.18.

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Set the priority version

Provide a priority number for update-alternatives. Higher numbers = higher priority: 
Enter the Java version
2100
Best practice for version numbers:
  • Java 21: 2100
  • Java 17: 1700
  • Java 11: 1100
  • Java 8: 800
This ensures the newest version has the highest priority by default.

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What happens behind the scenes

JavaOptionsCli performs these operations:
  1. Extracts the .tar.gz file to the current directory
  2. Moves the extracted folder to /opt/java/
  3. Registers three binaries with update-alternatives:
    • /opt/java/jdk-21/bin/java → /usr/bin/java
    • /opt/java/jdk-21/bin/javac → /usr/bin/javac
    • /opt/java/jdk-21/bin/jar → /usr/bin/jar

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Step 5: Switch between Java versions

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Use the change version feature

From the main menu, select Changes Version. You’ll be prompted three times to configure:
  1. The active java binary
  2. The active javac compiler
  3. The active jar tool
For each prompt, select the version number you want to activate.
The tool runs update-alternatives --config for each binary. Choose the same version for all three to avoid mismatches between runtime and compiler.

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Verify the active version

After switching, verify your Java version: 
java -version
javac -version

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Step 6: View installed versions

Select View List Versions from the menu to see all Java installations registered with update-alternatives. This displays:
  • All registered java binaries
  • All registered javac compilers
  • All registered jar tools

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Step 7: Remove a Java version (optional)

To uninstall a Java version:
  1. Select Delete Version from the menu
  2. Enter the folder name (e.g., jdk-21)
  3. Choose whether to delete the physical files from /opt/java
The tool will:
  • Remove the version from update-alternatives
  • Optionally delete the installation directory
Deletion is permanent. Ensure you’re removing the correct version before confirming.

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Best practices

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Organize your downloads

Keep all Java tar.gz files in a dedicated directory for easy access: 
~/java-downloads/
├── jdk-21_linux-x64_bin.tar.gz
├── jdk-17_linux-x64_bin.tar.gz
└── jdk-11_linux-x64_bin.tar.gz

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Use consistent naming

When extracting, Java archives typically create folders like:
  • jdk-21.0.2
  • jdk-17.0.1
  • jdk-11.0.18
Use these exact names when prompted by JavaOptionsCli.

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Set appropriate priorities

Use priority numbers that reflect the version hierarchy. This ensures update-alternatives --auto selects the most recent version by default.

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Keep runtime and compiler in sync

Always set the same Java version for java, javac, and jar to avoid compatibility issues.

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Common workflows

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Install multiple versions for testing

# Install Java 21 (priority 2100)
# Install Java 17 (priority 1700)
# Install Java 11 (priority 1100)

# Default will be Java 21
java -version  # 21.0.2

# Switch to Java 17 for legacy project
JavaOptionsCli → Changes Version → Select 1700
java -version  # 17.0.1

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Update to a newer patch version

# Install new version with higher priority
# Example: Upgrading from 21.0.1 to 21.0.2

# Install 21.0.2 with priority 2101
JavaOptionsCli → New Version Java

# Remove old version
JavaOptionsCli → Delete Version → jdk-21.0.1

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Verify installation integrity

After installation, verify all components: 
which java    # /usr/bin/java
which javac   # /usr/bin/javac
which jar     # /usr/bin/jar

ls -l /usr/bin/java   # Should point to /etc/alternatives/java
ls -l /etc/alternatives/java  # Should point to /opt/java/jdk-XX/bin/java

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