Inheritance - Java - page 431

The line with this is an invocation of the constructor with the following heading:

public HourlyEmployee(String theName, Date theDate,
double theWageRate, double theHours)

The restrictions on how you can use the base class constructor call super also apply
to the this constructor. You cannot use an instance variable as an argument to this .
Also, any call to the constructor this must always be the first action taken in a con-
structor definition. Thus, a constructor definition cannot contain both an invocation
of super and an invocation of this . If you want to include both a call to super and a
call to this , use a call with this , and have the constructor that is called with this have
super as its first action.

Call to Another Constructor in the Same Class
Within the definition of a constructor for a class, you can use this as a name for another
constructor in the same class. Any invocation of this must be the first action taken by the
constructor.
EXAMPLE
public HourlyEmployee()
{
this ("No name", new Date("January", 1, 1000), 0, 0);
}

TIP: An Object of a Derived Class Has More than One Type

An object of a derived class has the type of the derived class, and it also has the type
of the base class, and more generally, has the type of every one of its ancestor classes.
For example, consider the following copy constructor definition from the class
HourlyEmployee (Display 7.3):

public HourlyEmployee(HourlyEmployee originalObject)
{
super (originalObject);
wageRate = originalObject.wageRate;
hours = originalObject.hours;
}

(continued)