AddressBook-Level3 (AB3) is a brownfield project template used by SE courses. Given below are some tutorials to help students understand how to navigate and modify the existing AB3 codebase.
Tracing code - A tutorial on how to use Intellij IDEA to trace execution paths in AB3 code.
Adding a command - A tutorial on how to introduce a new user command to the AB3 code.
Removing fields - A tutorial on how to safely remove a field of the Person class.