Code is read more often than it is written. Notebooks, especially, are made to be looked at. Assist yourself and others by keeping your code and notebooks neat!
Naming conventions and other good Java practices are listed in the Java Documentation.
Also see these naming conventions. Although the information on this document has not been updated in ages, the content is still relevant to the conventions that are still used today.
Look at this section of this Java tutorial to acquaint yourself with best coding practices for Java.
Here’s a good conceptualisation of how git works in a development team. There are different ways for team to work, but this Atlassian Git Workflow article gives you a great introduction.
You can thank me later ;)