chapter 8: Saving Time and Money:Reusing Existing Code
8.1 Defining a Class (What It Means to Be an Employee)
8.2 Working with Disk Files( a Brief Detour)
8.3 Defining Subclasses(What It Means to Be a Full-Time or Part-Time Employee
8.4 Using Subclasses
8.5 Overriding Existing Methods(Changing the Payments for Some Employees)