Java Reference
In-Depth Information
}
public static void main(String[] args)
{
Truck truck = new Truck("Chevrolet", "Silverado",
2011, true);
System.out.println("Make = "+truck.getMake());
System.out.println("Model = "+truck.getModel());
System.out.println("Year = "+truck.getYear());
System.out.println("Extended
cab
=
"+truck.isExtendedCab);
}
}
model,andyear;aconstructorthatinitializesthesefieldstopassedarguments;andget-
ter methods that retrieve these fields' values.
The
Car
subclassprovidesa
private numWheels
field,aconstructorthatinitial-
izes a
Car
object's
Vehicle
and
Car
layers, and a
main()
class method for test-
ingthisclass.Similarly,the
Truck
subclassprovidesa
private isExtendedCab
field,aconstructorthatinitializesa
Truck
object's
Vehicle
and
Truck
layers,and
a
main()
class method for testing this class.
Car
'sand
Truck
'sconstructorsusereservedword
super
tocall
Vehicle
'scon-
structorwith
Vehicle
-orientedarguments,andtheninitialize
Car
's
numWheels
and
Truck
's
isExtendedCab
instancefields,respectively.The
super()
callisanalog-
ous to specifying
this()
to call another constructor in the same class, but invokes a
superclass constructor instead.
Caution
The
super()
callcanonlyappearinaconstructor.Furthermore,itmust
bethefirstcodethatisspecifiedintheconstructor.If
super()
isnotspecified,andif
thesuperclassdoesnothaveanoargumentconstructor,thecompilerwillreportanerror
because the subclass constructor must call a noargument superclass constructor when
super()
is not present.
Car
's
main()
methodcreatestwo
Car
objects,initializingeachobjecttoaspecific
make, model, year,andnumberofwheels. Four
System.out.println()
method
callssubsequentlyoutputeachobject'sinformation.Similarly,
Truck
's
main()
meth-
od creates a single
Truck
object, and also initializes this object to a specific make,
