Java-- is a simpler version of Java aiming to teach programming.
Starting from version 1.7.0, Java-- requires Java 8.
You can either install Java-- SDK into an existing Eclipse or download a pre-configured Eclipse distribution with Java-- installed (choosing the one for your operating system).
Eclipse update site
Copy the following URL and paste it into your Eclipse "Install New Software" dialog ("Help" => "Install New Software..."), wait for the list of available features to show and select the latest version of "Javamm SDK feature". (The URL is NOT meant to be opened with a browser). TIP: use the "type filter text" to quickly filter the features, e.g., start typing "Javamm".
IMPORTANT: Java-- requires Xtext, if this is not already installed, all dependencies will be automatically installed form this update site, which is self-contained.
Pre-configured Eclipse distributions with Java-- installed, for several architectures.
Download a complete Eclipse distribution with Java-- installed; choose the one for your OS and architecture: https://sourceforge.net/projects/javamm/files/products/