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The View List Versions command displays all Java versions registered with the system’s alternatives system, showing the complete paths to each installation.

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When to use this command

Use this command when you:
  • Want to see what Java versions are available on your system
  • Need to verify a Java version was installed correctly
  • Are checking which versions are registered before deleting one
  • Want to know the exact paths to your Java installations
  • Need to audit your system’s Java configurations

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How it works

This command uses update-alternatives --list to query all registered alternatives for the three Java binaries: java, javac, and jar.

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Step-by-step usage

1

Select the command

From the main menu, choose “View List Versions”
2

View Java runtime versions

The tool displays all registered java alternatives:
Showing versions

Showing Java versions
/opt/java/jdk-11/bin/java
/opt/java/jdk-17/bin/java
/opt/java/jdk-21/bin/java
3

View javac compiler versions

Next, it shows all javac alternatives:
Showing javac versions
/opt/java/jdk-11/bin/javac
/opt/java/jdk-17/bin/javac
/opt/java/jdk-21/bin/javac
4

View jar tool versions

Finally, it displays jar alternatives:
Showing jar versions
/opt/java/jdk-11/bin/jar
/opt/java/jdk-17/bin/jar
/opt/java/jdk-21/bin/jar

Press Enter to continue...
5

Return to menu

Press Enter to return to the main menu.

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What happens behind the scenes

The implementation in internal/commands/listjavaversion.go:10-42 executes three update-alternatives --list commands: 
color.Info.Prompt("Showing Java versions")
err := u.RunCommandInteractive("update-alternatives", "--list", "java")
if err != nil {
    color.Error.Println("Error: ", err)
    return
}

fmt.Print("\n")

color.Info.Prompt("Showing javac versions")
err = u.RunCommandInteractive("update-alternatives", "--list", "javac")
if err != nil {
    color.Error.Println("Error: ", err)
    return
}

color.Info.Prompt("Showing jar versions")
err = u.RunCommandInteractive("update-alternatives", "--list", "jar")
if err != nil {
    color.Error.Println("Error: ", err)
    return
}
Each command queries the alternatives database and returns the full paths to all registered versions of that binary.

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Real terminal example

$ javaoptionscli
# Select "View List Versions" from menu

Showing versions

Showing Java versions
/opt/java/jdk-11/bin/java
/opt/java/jdk-17/bin/java
/opt/java/jdk-21/bin/java


Showing javac versions
/opt/java/jdk-11/bin/javac
/opt/java/jdk-17/bin/javac
/opt/java/jdk-21/bin/javac
Showing jar versions
/opt/java/jdk-11/bin/jar
/opt/java/jdk-17/bin/jar
/opt/java/jdk-21/bin/jar

Press Enter to continue...

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Understanding the output

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Path structure

Each path follows this pattern: 
/opt/java/[folder-name]/bin/[binary]
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/opt/java
directory
The standard installation directory for all Java versions managed by JavaOptionsCli
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[folder-name]
directory
The specific Java version directory (e.g., jdk-11, jdk-17, jdk-21-oracle)
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bin/[binary]
executable
The actual Java binary (java, javac, or jar)

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What if versions don’t match?

Ideally, all three lists should show the same set of Java versions. If they don’t match:
If you see different versions listed for java, javac, and jar, it indicates an incomplete installation. This can happen if:
  • A previous installation was interrupted
  • A version was manually removed from the alternatives system
  • Files were deleted from /opt/java/ without unregistering
Use the Delete Version command to clean up inconsistent entries.

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Common use cases

Before installing a new Java version, check what’s already installed:
$ javaoptionscli
# Select "View List Versions"
# Review the list
# If version already exists, no need to reinstall
After installing a new Java version, confirm it was registered:
$ javaoptionscli
# Select "New Version Java" and complete installation
# Return to menu and select "View List Versions"
# Verify new version appears in all three lists
Save the list for documentation or troubleshooting:
$ update-alternatives --list java > installed-java-versions.txt
$ update-alternatives --list javac >> installed-java-versions.txt
$ update-alternatives --list jar >> installed-java-versions.txt
Cross-reference registered versions with actual directories:
$ javaoptionscli  # View List Versions
$ ls -la /opt/java/
# Check if directories match registered versions

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Difference from Change Version command

While both commands show Java versions, they serve different purposes:
List VersionsChange Version
Shows only pathsShows paths, priorities, and status
Read-only operationAllows switching versions
No sudo requiredRequires sudo privileges
Quick referenceInteractive configuration
Use List Versions for a quick check of what’s installed. Use Change Version when you need to see priorities and actually switch versions.

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Troubleshooting

Empty list displayed
  • No Java versions are registered in the alternatives system
  • Install Java using the New Version Java command
Error: update-alternatives: command not found
  • Your system doesn’t have the update-alternatives tool
  • This typically indicates a non-Debian/Ubuntu system
  • JavaOptionsCli is designed for Debian-based Linux distributions
Versions listed but java -version shows different version
  • Your JAVA_HOME environment variable may be set to a different installation
  • Check with: echo $JAVA_HOME
  • Use Change Version to update system-wide defaults

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