Now, square( ) will return the square of whatever value it is called with. That is, square( ) is
now a general-purpose method that can compute the square of any integer value, rather than
just 10.
Here is an example:
int
x, y;
x=
square(5); // x equals 25
x=
square(9); // x equals 81
y=
2;
x=
square(y); // x equals 4
In the first call to square( ), the value 5 will be passed into parameter i. In the second call, i
will receive the value 9. The third invocation passes the value of y, which is 2 in this example.
As these examples show, square( ) is able to return the square of whatever data it is passed.
It is important to keep the two terms parameter and argument straight. A parameter is a
variable defined by a method that receives a value when the method is called. For example,
in square( ), i is a parameter. An argument is a value that is passed to a method when it is
invoked. For example, square(100) passes 100 as an argument. Inside square( ), the parameter i
receives that value.
You can use a parameterized method to improve the Box class. In the preceding examples,
the dimensions of each box had to be set separately by use of a sequence of statements, such as:
mybox1.width = 10;
mybox1.height = 20;
mybox1.depth = 15;
While this code works, it is troubling for two reasons. First, it is clumsy and error prone. For
example, it would be easy to forget to set a dimension. Second, in well-designed Java programs,
instance variables should be accessed only through methods defined by their class. In the
future, you can change the behavior of a method, but you can't change the behavior of an
exposed instance variable.
Thus, a better approach to setting the dimensions of a box is to create a method that takes
the dimensions of a box in its parameters and sets each instance variable appropriately. This
concept is implemented by the following program:
// This program uses a parameterized method.
class Box {
double width;
double height;
double depth;
// compute and return volume
double volume() {
return width * height * depth;
}
// sets dimensions of box
void setDim(double w, double h, double d) {
width = w;
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