Java Reference
In-Depth Information
In the program, notice that when
range( )
is called, it is put on the right side of an as-
signment statement. On the left is a variable that will receive the value returned by
range(
)
. Thus, after
executes, the range of the
minivan
object is stored in
range1
.
Notice that
range( )
now has a return type of
int
. This means that it will return an integer
value to the caller. The return type of a method is important because the type of data re-
turned by a method must be compatible with the return type specified by the method. Thus,
if you want a method to return data of type
double
, its return type must be type
double
.
Although the preceding program is correct, it is not written as efficiently as it could be.
Specifically, there is no need for the
range1
or
range2
variables. A call to
range( )
can be
used in the
println( )
statement directly, as shown here:
In this case, when
println( )
is executed,
minivan.range( )
is called automatically and its
value will be passed to
println( )
. Furthermore, you can use a call to
range( )
whenever
the range of a
Vehicle
object is needed. For example, this statement compares the ranges of
two vehicles:
Using Parameters
It is possible to pass one or more values to a method when the method is called. Recall that
a value passed to a method is called an
argument
. Inside the method, the variable that re-
ceives the argument is called a
parameter
. Parameters are declared inside the parentheses
that follow the method's name. The parameter declaration syntax is the same as that used
for variables. A parameter is within the scope of its method, and aside from its special task
of receiving an argument, it acts like any other local variable.
Here is a simple example that uses a parameter. Inside the
ChkNum
class, the method
isEven( )
returns
true
if the value that it is passed is even. It returns
false
otherwise. There-
fore,
isEven( )
has a return type of
boolean
.
