Just to clarify a little more, a variable will only be visible in the
block in which you declare it. So when you go
public static int prduct(int x, int y)
{
int mult;
mult = (x * y);
return mult;
}
the mult variable is only visible between the { and } and the caller
will not be able to it or any other variable inside your function.
This gives you the freedom to change the variables inside your
function without introducing changes into the calling code (this is
called block scoping, not all languages do it but most do).
I usually explain this to people using the following example from
mathematics:
Let a=1 and b=f(x)
Question, what is the value of a?
It's not a trick question, the value of course is 1. In a computer
program though, the answer is not obvious, f() might change the value
of a.
What is the lesson? The lesson is that when you call a function, it
should compute some result and return it, it shouldn't compute some
result and store it in a variable. There will be exceptions to this
rule; sometimes your function must change a value. When this happens,
the name of the function should convey the fact that something will
change, often by calling it setSomething().
Finally, a note about your naming. You have created a function called
prduct(), most people can figure out that this means product() but why
not just call it product() anyway. People used to abbreviate function
names because there were limits to how long your variable and function
names could be (I still work with some old code which limits variables
to 10 characters) but today, your variable and function names can be
as long as you like.
-phil
On May 28, 3:07 am, Luke Vandervort <[email protected]> wrote:
> Hi guys, hope you don't mind me asking a question! Can anyone tell me why
> variable mult is not returning to the main method? Everything else works
> great! Excuse my ignorance I am just learning this! Thanks!
>
> public class Numbers
> {
>
> public static void main(String[] args)
> {
> int a = 20;
> int b = 67;
>
> mysum(a, b);
> mydifference(a, b);
> prduct(a, b);
>
> System.out.println("The product of a * b = " + mult);
> }
> public static void mysum(int x, int y)
> {
>
> int newsum;
> newsum = (x + y);
> System.out.println("The sum of a and b = " + newsum);
> }
> public static void mydifference(int x, int y)
> {
> int newdifference;
> newdifference = (x - y);
> System.out.println("The difference between a and b = " +
> newdifference);
> }
>
> public static int prduct(int x, int y)
> {
> int mult;
> mult = (x * y);
> return mult;
> }
> }
>
> --
> Luke M. P. Vandervort
>
> — Philippians 3:18-19
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