You can skip this step. The instructions I gave to get set up with Github Codespaces should have given you an environment where Java is already set up.

Download the "JDK MSI" from adoptium.net. Select whatever the newest version is. You will need at least Java 25 to follow along with the examples in this book.

Run the installer, selecting all the default options. This should make the java command available to you.

Download the "JDK .pkg" from adoptium.net. Select whatever the newest version is. You will need at least Java 25 to follow along with the examples in this book.

Run the installer, selecting all the default options. This should make the java command available to you.

Linux is a little annoying. If you are using it you are likely used to it by now, but you can use adoptium.net like everyone else, but there is no universal installer there.

You can either download the .tar.gz file that matches your machine, extract it, and add the bin folder to your PATH, or you can try to find an installer for your specific linux distribution.