Question

First example

int windowStart = 0;

for (int i = 0; i + windowSize < fileArray.size(); i++) {
  ArrayList <Character> window = new ArrayList <Character> ();
  for (int s = windowStart; s <= windowStart + windowSize; s++) {
    window.add(fileArray.get(s));
  }
  windowStart++;
}

VS.

second example

int ind = 0;
for (int i = 0; i + windowSize < fileArray.size(); i++) {
  for (int b = ind; b <= windowSize + ind; b++) {
    window.add(fileArray.get(b));
  }
  ind++;
}

The first one throws an java.lang.IndexOutOfBoundsException while the second one does not and works just fine. fileArray is the same for both, but for 2. the window array is defined as an attribute, while for the first one, the “window” array is defined inside the method (and the for loop). Does that make a difference?

Answer 1

You can’t get an IndexOutOfBoundsException for adding a value to a list. The problem is that a value of s is equal or greater then the actual size of the fileArray array or list.

And because the loops in both examples are equivalent, the problem should be found outside the lines of code you’ve just posted.

Try to debug (break on IndexOutOfBoundsException if you are using an IDE, otherwise add some simple System.out.println statements to find out, why s is greater than expected.