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Asked: 2024-09-27T07:50:23+05:30 In:

How can I configure my system to use a specific version of Java as the default on Ubuntu?

I’ve been diving deep into some Java development lately, and I really need your help with something that’s been bugging me for a while. So here’s the deal: I’ve got multiple versions of Java installed on my Ubuntu setup. It’s kind of a mess, to be honest. I initially installed Java 8 for some legacy projects, but then I upgraded to Java 11, and now I’m trying to start a new project that actually requires Java 17. Yeah, I know—it’s chaotic.

The thing is, I keep running into issues because my system defaults to Java 8 whenever I run any Java command. I thought I could just update the alternatives or something like that, but honestly, I’m not entirely sure how to go about it. I’ve tried a couple of commands, but I keep getting conflicting results, and now I’m at a point where I’m super confused.

Could someone explain how to configure my system to use a specific version of Java as the default? Like, what are the exact commands I need to run? Also, what should I check if things don’t seem to work right afterward? Do I need to change any environment variables or something?

I’m worried that if I set it up incorrectly, I might break something in my current setups. It feels like I’m walking on eggshells, especially since I still need to work on that old code that uses Java 8 and ensure nothing gets disrupted.

Plus, if someone could give me a step-by-step guide or maybe some tips on keeping it all organized, that would be amazing. Like, is there a best practice for managing multiple Java versions on Ubuntu? Should I uninstall the old versions, or can I keep them around just in case?

I’m really grateful for any advice you can throw my way. Dealing with versioning is one of those things that makes you want to tear your hair out sometimes!

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    2 Answers



    1. Managing Multiple Java Versions on Ubuntu

      How to Set Up Multiple Java Versions on Ubuntu

      Sounds like you’re in a bit of a Java jam! No worries, I’ve got your back. Here’s a step-by-step guide to help you set your default Java version using update-alternatives, and some tips for keeping your setup organized.

      Step 1: Check Installed Java Versions

      First, let’s see what Java versions you have installed. Open your terminal and run:

      ls /usr/lib/jvm/

      This will show all the Java installations on your system. You should see directories for Java 8, Java 11, Java 17, etc.

      Step 2: Use update-alternatives

      Next, you can use update-alternatives to set the default version. You’ll need superuser access for this:

      sudo update-alternatives --config java

      You’ll see a list of all the Java versions you have installed along with their path and a selection number. Just type the number corresponding to the version you want to set as default (e.g., Java 17) and hit Enter.

      Step 3: Set JAVA_HOME (if needed)

      Some applications check the JAVA_HOME environment variable, so it might be a good idea to set it. You can do this by adding the following line to your ~/.bashrc (or ~/.bash_profile) file:

      export JAVA_HOME=/usr/lib/jvm/jdk-17

      Make sure to replace /usr/lib/jvm/jdk-17 with the actual path to your Java 17 installation. After editing the file, run:

      source ~/.bashrc

      Step 4: Verify Everything Works

      Now, check which Java version is running by typing:

      java -version

      This should show the Java version you set as default. If it still shows Java 8, you might want to repeat Step 2 and make sure you selected the right one.

      Step 5: Tips for Managing Multiple Versions

      • Keep all versions installed unless you’re sure you don’t need them. It’s good to have options for legacy projects.
      • You can create scripts or aliases in your ~/.bashrc to switch Java versions quickly if you need to.
      • Consider using a version manager for Java, like SDKMAN!, that can help streamline switching between different Java versions easily.

      Final Thoughts

      Just take it one step at a time, and remember, it’s better to check that everything’s working after you make changes rather than rush through it. Good luck, and I hope this makes your Java journey a bit smoother!




    2. Managing Multiple Java Versions on Ubuntu

      To manage multiple versions of Java on your Ubuntu system, you can use the `update-alternatives` command. This allows you to set the default Java version conveniently. First, check the installed Java versions by running:

      sudo update-alternatives --config java

      This will display a list of all the Java installations on your system. You will see a selection number next to each version. Simply type the number corresponding to the version you want to set as default (in your case, Java 17) and press Enter. After setting it, verify the configuration with:

      java -version

      If you need to set the JAVA_HOME environment variable, you can add the following lines to your `~/.bashrc` or `~/.profile` file:

      export JAVA_HOME=/usr/lib/jvm/java-17-openjdk-amd64
export PATH=$JAVA_HOME/bin:$PATH

      After editing, run `source ~/.bashrc` to apply the changes. If you encounter any issues, check that the correct paths are set in your environment variables, and confirm that no conflicting configurations exist in the `.bashrc` or any other shell configuration files. Keeping older versions of Java around is fine for legacy projects; just ensure you manage the selection properly to avoid conflicts.


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