When I go to https://github.com/google/gson I can only download the library as a zip folder as opposed to a jar file.
Where can I get the jar file?
First you need to clone the repository locally on your computer:
git clone https://github.com/google/gson
Then you go inside the project folder ./gson and you create the jar file running:
mvn package
Of course to do this you need to have maven installed, if you are under osx you can install it running
brew install maven
Otherwise you can look for the installation for your system on the maven official website
After running mvn package the jar file will be in ./gson/gson/target/gson-2.7.1-SNAPSHOT.jar