scope of variables in functions

[tmwhalens]

my problem is this:
i am comparing two arrays with a for loop. in each iteration, if there is a match i want to increment iCorrect by one. if there is NOT a match i want to increment iWrong by one. however, after the loops have terminated i can not access the values of variables iCorrect and iWrong. why? must i use an array for storing the number of correct and incorrect responses?
thanx,
thomas
PS. i am sticking in some code to show that i have attemtpted this problem:

/* block of code */
/* initialize arrays */
int[] arrayA;   // answers
int[] arrayB;   // responses

/* size up arrays */
arrayA = new int[5];
arrayB = new int[5];

/* populate arrays here */
..........

/* correct, wrong counters */
int iCorrect = 0;
int iWrong = 0;

/* check answers for correctness */
for(int i=0; i<5; i++)
{
   if(arrayA[i] == arrayB[i])
   {
      iCorrect++;
   }
   else
   {
      iWrong++;
   }   
}

/* print out results of quiz */
System.out.print(
   "\nCorrect: " + iCorrect +
   "\nWrong: " + iWrong
);

[This message has been edited by tmwhalens (edited November 08, 2001).]
[This message has been edited by tmwhalens (edited November 08, 2001).]
[This message has been edited by tmwhalens (edited November 08, 2001).]

[Junilu Lacar]

Thomas,
Thanks for making the effort to format your code to make it nice and readable
I can't see anything in the code that would make it print incorrect results and my own test of this code gives me the correct results.
Some nit-picking:
- instead of naming the arrays "arrayA" and "arrayB" then adding comments about what they are, just name them "answers" and "responses". Makes the code much more readable.
- instead of hard-coding the size of the array (in this case 5, but that could change, right?), either declare a static final int NUM_QUESTIONS and use that throughout the code or just declare and initialize in the same statement, e.g.
int[] answers = {1, 2, 3, 4, 5};

- In the for-loop, it is better to use the actual array.length in the loop condition, e.g.:
for (int i = 0; i < arrayA.length; i++) { ... }
This way, if you decide to change the array size, you'll have less code to change.
Good luck!
Junilu

[Thomas Whalen]

Junilu,
Thanks for the advice! Is it better to use the ArrayName.length property in a function << or >> use that property outside of the function? I was wondering if it might make a difference in regards to overall speed, even though speed is not going to be a factor for such a simple, small program.
Thanks,
Thomas

[Junilu Lacar]

Thomas,
Not sure if this is what you mean by "in" or "out" of a function but I'll take a stab:
<pre>
// is this better...
// #1
int len = array.length;
for (i = 0; i < len; i++) {...}
// ...than this?
// #2
for (i = 0; i < array.length; i++) {...}
</pre>
I don't think you gain anything with #1. Plus, you have an additional temporary variable. In his book "Refactoring", Martin Fowler often advises against using temporary variables like this and actually has a Refactoring called "Replace Temp with Query", which basically refactors #1 to #2.

------------------
Junilu Lacar
Sun Certified Programmer for the Java� 2 Platform

[Thomas Whalen]

Thanks Junilu! I will work on keeping excessive temporary variables to a minimum
Thomas

[William Barnes]

There is nothing wrong with the code. Try putting print statements where iCorrect and iWrong are incremented to see which block is being hit.