Teach object orientation with Java

Greenfoot 3.9.0 (29. October 2024)$$$$$$Upgraded to Java 21 including support for new language features.$$$Added code completion for local variables.$$$Fixed bug with compiler errors sometimes not showing.$$$Improved Mac startup speed (especially on new Apple Silicon build).$$$Added Raspberry Pi Linux build.$$$Several Java and Stride editor bug fixes.$$$Fixed a bug where the Windows MSI installer would allow multiple per-machine installations of different versions (in the same directory). Greenfoot 3.9.0 should correctly remove all prior per-machine installations of earlier Greenfoot versions.

Greenfoot 3.8.2 (1. December 2023)$$$$$$Fixed Share to website function so that it works with new scenarios.$$$Removed ability to share to standalone JAR.

Greenfoot 3.8.1 (3. November 2023)$$$$$$Added the new Actor.sleepFor(int) method.$$$Fixed Import Class dialog (was empty on some operating systems).$$$Fixed Greenfoot class documentation not showing on some operating systems.$$$Fixed About dialog and file-open not working on Mac after certain actions.

Greenfoot 3.7.1 (12. May 2022)$$$$$$Bug fixes in Java and Stride editors.$$$Added autocomplete support for Greenfoot.isKeyDown (and similar static methods) by just completing on Gr and similar.$$$Fixed Actor/World documentation not showing up on Linux.$$$Tidied up items on help menu