[root tip] [How To] I have downloaded a program as a jar file - what now?

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1

Difficulty: ★☆☆☆☆

What is a jar file

A jar is java package - a zip-compressed archive - including the code for a java application.

How can I start the application

The jar requires at least JRE (Java Runtime Environment) - some requires the full JDK (Java Development Kit). A JDK contains the corresponding JRE.

If in doubt of the actual requirements of the application - install the JDK.

To install the latest JRE

sudo pacman -Syu jre-openjdk

Or the complete environment

sudo pacman -Syu jdk-openjdk

Commandline

To run the application contained in the jar

java -jar java-app.jar

Create a script and a launcher

If you want to launch the program from your menu or the terminal - create a script and a launcher as follows.

  1. Create the bin folder

    mkdir ~/.local/bin

  2. Move the jar to the bin folder
    Assuming it is in Downloads

    mv ~/Downloads/java-app.jar ~/.local/bin

  3. Create the script
    Open your favorite text editor with a new file and save it as ~/.local/bin/java-app with below content - the “$@” ensures that any arguments to the script is passed on to the java-app.jar file

    #!/bin/sh
java -jar ~/.local/bin/java-app.jar "$@"

  4. Make the script executable

    chmod +x ~/.local/bin/java-app

  5. Create the application folder

    mkdir -p ~/.local/share/applications

  6. Create the desktop launcher
    Use the text editor to create a new file and save it as ~/.local/share/applications/java-app.desktop with below content

    [Desktop Entry]
Encoding=UTF-8
Name=Some Java App
Comment=Run the java-app.jar program
GenericName=Some Java App
Exec=~/.local/bin/java-app
Terminal=false
Type=Application
Icon=java-app-icon
Categories=Application;
StartupWMClass=java-app
StartupNotify=true

Conclusion

You are now be able to run Some Java App by providing the script name and any arguments for the java-app.jar and you can find it in the system’s menu tree.

8 Likes
2

Thank you for this great tutorial!

I could add additional step how to change current Java environment (granted you have more than one).

  1. Check available Java environments:
    archlinux-java status

Example output:

Available Java environments:
  java-11-openjdk
  java-14-openjdk
  java-8-openjdk/jre (default)
  1. Set new Java environment:
    sudo archlinux-java set java-11-openjdk

Result:

Available Java environments:
  java-11-openjdk (default)
  java-14-openjdk
  java-8-openjdk/jre
2 Likes
3

I followed the instructions above, but when I try to open the launcher I get an error:
“Failed to execute child process “path/to/java-app” (No such file or directory)”

I’ve quadruple-checked to make sure that the path and filename to the script is correct in the .desktop file are correct.