Grouping attributes associated with students, units, and enrolment into three separate classes.

Ensuring that the fields in the Unit class cannot be directly accessed from outside that class, but only via methods.

In reality, a course unit has lots of different attributes (e.g. prerequisites, assessments, learning outcomes), but only three are represented in the Unit class.

Using the private access modifier when defining fields such as name, address, phoneNo, and email.