Re: Error message
sdlt85@gmail.com wrote:
//Hi, I need some help.
//I am having a error message stating "cannot find symbol variable
stop" where the arrow is.
The concept in question is called "scope". Your variable didn't have the
right scope. Let's break that down.
Scope is more or less a range between braces. Something declared before the
block is visible, i.e., "in scope", within the braces. Something declared
within the braces is only visible from there to the end of the block.
That's the simple version, and enough for now. Let's go through the code to
where that matters.
import java.util.Scanner;
public class IntegerSetTest
{
public static void main(String[] args)
Do not use TABs in Usenet posts.
{
Scanner input = new Scanner (System.in);
The variable 'input' is now in scope from here to the end of main(), and no
further.
System.out.println("Welcome to the Integer Set\n");
System.out.println("This program is going to find the union or "
+ "intersection of any two sets you enter.\nAlso it will delete "
+"or insert an element and check if the sets are equal." +
"\nPlease enter the number of sets: ");
int intArray[] = new int[100];
Avoid variable names that are tightly tied to the implementation. Names
should make sense in the problem domain.
int value;
Variable 'value' now in scope until the end of main(), and no further.
try
{
do
{
int i;
In scope until the end of the inside of the 'do..while' loop, only.
But - and this is a really big "but" - no value is assigned to it.
value = input.nextInt();
Scope started before the 'try' block.
intArray [i] = value;
This line shouldn't compile. Didn't it give you an error?
'i' is not "definitely assigned" at this point, so you cannot dereference it.
System.out.println("Enter -1 to finish: ");
int stop = input.nextInt();
In scope until the end of the inside of the do..while loop, only.
i++;
'stop' and 'i' are out of scope now. (Well, almost.)
That means that 'i' the next time around the loop will never be incremented
here - its scope is too narrow.
}
Well, really, they're out of scope *now*, but the thing is that the 'i' inside
the loop is a new one each time around the loop. It's scope expires with each
iteration. Same with 'stop'.
while( stop != -1 );
Whoops! stop is not in scope.
for ( int i = 0; i < intArray.length; i++ )
{
System.out.println( intArray [i] );
}
}
catch ( NumberFormatException ex )
{
Of course, in Real Life you would never, never, never omit exception handling.
Or logging.
}
}
}
<http://www.physci.org/codes/sscce.html>
--
Lew