While working with the branch, you need to periodically update your branch with new data from the main development branch. The operation is not the most basic and does not always go smoothly and simply, but it is extremely important.
Let me remind you:
the project source codes are on GitHub. Details in "Issue 16. Where to get the program texts?"
for those who have already watched, direct links:
https://github.com/java-webinars/java... and https://github.com/java-webinars/ext-...
you can watch a simpler project at the link http://java-course.ru/begin/