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In-Depth Information
b)
Assume that the following line of code appears before a method declaration:
@Override
c)
Assume that the following line of code appears as the first statement in a constructor's
body:
super
(firstArgument, secondArgument);
9.10
(Write a Line of Code)
Write a line of code that performs each of the following tasks:
a) Specify that class
PieceWorker
inherits from class
Employee
.
b) Call superclass
Employee
's
toString
method from subclass
PieceWorker
's
toString
method.
c) Call superclass
Employee
's constructor from subclass
PieceWorker
's constructor—as-
sume that the superclass constructor receives three
String
s representing the first name,
last name and social security number.
9.11
(Using
super
in a Constructor's Body)
Explain why you would use
super
in the first state-
ment of a subclass constructor's body.
9.12
(Using
super
in an Instance Method's Body)
Explain why you would use
super
in the body
of a subclass's instance method.
9.13
(Calling
get
Methods in a Class's Body)
In Figs. 9.10-9.11 methods
earnings
and
to-
String
each call various
get
methods within the same class. Explain the benefits of calling these
get
methods within the classes.
9.14
(
Employee
Hierarchy)
In this chapter, you studied an inheritance hierarchy in which class
BasePlusCommissionEmployee
inherited from class
CommissionEmployee
. However, not all types of
employees are
CommissionEmployee
s. In this exercise, you'll create a more general
Employee
superclass
that
factors out
the attributes and behaviors in class
CommissionEmployee
that are common to all
Em-
ployee
s. The common attributes and behaviors for all
Employee
s are
firstName
,
lastName
,
socialSe-
curityNumber
,
getFirstName
,
getLastName
,
getSocialSecurityNumber
and a portion of method
toString
. Create a new superclass
Employee
that contains these instance variables and methods and a
constructor. Next, rewrite class
CommissionEmployee
from Section 9.4.5 as a subclass of
Employee
.
Class
CommissionEmployee
should contain only the instance variables and methods that are not de-
clared in superclass
Employee
. Class
CommissionEmployee
's constructor should invoke class
Employee
's
constructor and
CommissionEmployee
's
toString
method should invoke
Employee
's
toString
method.
Once you've completed these modifications, run the
CommissionEmployeeTest
and
BasePlusCommis-
sionEmployeeTest
apps using these new classes to ensure that the apps still display the same results for
a
CommissionEmployee
object and
BasePlusCommissionEmployee
object, respectively.
9.15
(Creating a New Subclass of
Employee
)
Other types of
Employee
s might include
Salaried-
Employee
s who get paid a fixed weekly salary,
PieceWorker
s who get paid by the number of pieces
they produce or
HourlyEmployee
s who get paid an hourly wage with time-and-a-half—1.5 times the
hourly wage—for hours worked over 40 hours.
Create class
HourlyEmployee
that inherits from class
Employee
(Exercise 9.14) and has
instance variable
hours
(a
double
) that represents the hours worked, instance variable
wage
(a
dou-
ble
) that represents the wages per hour, a constructor that takes as arguments a first name, a last
name, a social security number, an hourly wage and the number of hours worked,
set
and
get
meth-
ods for manipulating the
hours
and
wage
, an
earnings
method to calculate an
HourlyEmployee
's
earnings based on the hours worked and a
toString
method that returns the
HourlyEmployee
's
String
representation. Method
setWage
should ensure that
wage
is nonnegative, and
setHours
should ensure that the value of hours is between 0 and 168 (the total number of hours in a week).
Use class
HourlyEmployee
in a test program that's similar to the one in Fig. 9.5.
