Inheritance - Java - page 429

Self-Test Exercises
1. Suppose the class named DiscountSale is a derived class of a class called Sale .
Suppose the class Sale has instance variables named price and numberOfItems .
Will an object of the class DiscountSale also have instance variables named price
and numberOfItems ?
2. Suppose the class named DiscountSale is a derived class of a class called Sale , and
suppose the class Sale has public methods named getTotal and getTax . Will an
object of the class DiscountSale have methods named getTotal and getTax ? If so,
do these methods have to perform the exact same actions in the class DiscountSale
as in the class Sale ?
3. Suppose the class named DiscountSale is a derived class of a class called Sale , and
suppose the class Sale has a method with the following heading and no other
methods named getTax :
public double getTax()
And suppose the definition of the class DiscountSale has a method definition
with the following heading and no other method definitions for methods named
getTax :
public double getTax( double rate)
How many methods named getTax will the class DiscountSale have and what are
their headings?
4. The class HourlyEmployee (Display 7.3) has methods named getName and getRate
(among others). Why does the definition of the class HourlyEmployee contain a def-
inition of the method getRate but no definition of the methods getName ?
There are some restrictions on how you can use the base class constructor call
super . You cannot use an instance variable as an argument to super . Also, the call to
the base class constructor ( super ) must always be the first action taken in a constructor
definition. You cannot use it later in the definition of a constructor.
Notice that you use the keyword super to call the constructor of the base class.
You do not use the name of the constructor; you do not use
Employee(theName, theDate); //ILLEGAL
If a constructor definition for a derived class does not include an invocation of a
constructor for the base class, then the no-argument constructor of the base class is
invoked automatically as the first action of the derived class constructor. So, the following