Object-Oriented Programming: Polymorphism and Interfaces - Java: How to Program Early Objects - page 414

27

28 this .baseSalary = baseSalary;

29 }

30
31

// return base salary

32

public double getBaseSalary()

33

{

34

return baseSalary;

35

}

36
37

// calculate earnings; override method earnings in CommissionEmployee
@Override
public double earnings()
{
return getBaseSalary() + super .earnings();
}

38

39

40

41

42

43
44

// return String representation of BasePlusCommissionEmployee object
@Override
public String toString()
{
return String.format( "%s %s; %s: $%,.2f" ,
"base-salaried" , super .toString(),
"base salary" , getBaseSalary());
}

45

46

47

48

49

50

51

52

} // end class BasePlusCommissionEmployee

Fig. 10.8 | BasePlusCommissionEmployee class extends CommissionEmployee . (Part 2 of 2.)

10.5.6 Polymorphic Processing, Operator instanceof and
Downcasting
To test our Employee hierarchy, the application in Fig. 10.9 creates an object of each of the
four concrete classes SalariedEmployee , HourlyEmployee , CommissionEmployee and Base-
PlusCommissionEmployee . The program manipulates these objects nonpolymorphically , via
variables of each object's own type, then polymorphically , using an array of Employee vari-
ables. While processing the objects polymorphically, the program increases the base salary
of each BasePlusCommissionEmployee by 10%—this requires determining the object's type
at execution time . Finally, the program polymorphically determines and outputs the type of
each object in the Employee array. Lines 9-18 create objects of each of the four concrete
Employee subclasses. Lines 22-30 output the String representation and earnings of each
of these objects nonpolymorphically . Each object's toString method is called implicitly by
printf when the object is output as a String with the %s format specifier.

1 // Fig. 10.9: PayrollSystemTest.java

2 // Employee hierarchy test program.

3
4 public class PayrollSystemTest

5 {

Fig. 10.9 | Employee hierarchy test program. (Part 1 of 4.)