How To Check and Uninstall Java Versions on Ubuntu

Java is a widely used programming language that powers a lot of applications and websites. If you’re using Ubuntu, it’s likely that you have Java installed on your system. In this article, we will guide you through the process of checking and uninstalling Java versions on Ubuntu.

Checking Java Versions

To determine which Java versions are installed on your system, you can use a series of commands. Let’s go through them one by one.

The update-java-alternatives -l Command

You can use the update-java-alternatives -l command to display all the Java versions installed on your system. The -l option stands for list, which will list all the Java alternatives in your system.

update-java-alternatives -l

The java -version Command

The java -version command will show you the Java version currently in use. The -version option is used to output version information.

java -version

The java -showversion Command

The java -showversion command will display the Java version in use along with additional information. The -showversion option is used to provide more detailed version information.

java -showversion

Checking Java Alternatives

Ubuntu uses an “alternatives” system to manage different versions of applications. You can use the following commands to check the Java virtual machine and compiler:

The file /etc/alternatives/java /etc/alternatives/javac Command

This command will show you what is currently providing the Java virtual machine (java) and the Java compiler (javac).

file /etc/alternatives/java /etc/alternatives/javac

The file which java javac“ Command

This command will check if the alternatives system is working properly and being used by Java. The which command is used to locate the executable file associated with the given command.

file `which java javac`

Uninstalling Java Versions

If you want to uninstall a specific version of Java, such as OpenJDK 6, you can use the command-line. Run the following command:

sudo apt-get remove openjdk-6-\* icedtea-6-\*

The sudo command is used to execute the command as an administrator. The apt-get remove command is used to remove the specified packages. The openjdk-6-\* and icedtea-6-\* are the packages to be removed.

Before removing any icedtea-6- or openjdk-6- packages, it is recommended to simulate the removal operation to check for any dependencies. You can do this by running:

apt-get -s remove openjdk-6-\* icedtea-6-\*

The -s option stands for simulate, which will simulate an operation but not actually perform it. This is useful for checking the potential impact of a command without actually executing it.

If you want to continue using Java content online in your web browser, make sure to have the corresponding icedtea-7- packages installed before removing any icedtea-6- or openjdk-6- packages.

Conclusion

In this article, we’ve covered how to check and uninstall Java versions on Ubuntu. Remember to always check for dependencies before uninstalling any packages to avoid breaking your system. If you have any questions or run into any issues, feel free to leave a comment below.