In Greenfoot 3.1.0 (the latest version) you can right-click a class in the diagram and choose to convert it to Java or Stride. You have to do this class by class, there is no simple way to do it for the whole project. I'm not sure if this possible in earlier versions. Java-to-Stride support was added in version 3.1.0. Stride support (generally) was added in version 3.0.

OK, that works. Thank you. From what I recall, was there not a button at the top-right corner of the editor which toggled the source code between java and stride? Perhaps I am mistaken. BTW, I noticed that stride does not support the ternary operator. Is there is list somewhere of java features which are not supported in stride? Thanks.

Sorry for the late answer. You can select a Java preview from the "view" menu in the editor, which doesn't do a permanent conversion but displays equivalent Java to the current Stride source (you cannot edit it). There's no list of java features not in Stride. A few features that are (or at least were not at some stage) supported are: lambdas, anonymous inner classes, annotations, floating point literals beginning with '.', pre- and post-increment/decrement operators, three-part "for" loops (Stride only has ranged-based for loops).

was meant.