why is the Arrayindex out of bound in the following code in java? I have checked the bounds but don't understand why/

Question

Arrayindex out of bounds error is showing up and I have particularly no idea why it is hapening. I am trying create 2N tuple objects and trying to put them in a array of size 2N

Tuple[] minuteunit = new Tuple[2*N];
if(!intervals.isEmpty())
{
    for(i = 0; i < ((2*N)-1); i = 1+2)
    {
        minuteunit[i] = new Tuple(intervals.get(i).getBeginMinuteUnit(),"s");
        minuteunit[i+1] = new Tuple(intervals.get(i).getEndMinuteUnit(),"e");
    }

Answer 1

it is most likely the face you are using i in intervals.get(i) , because i is incrementing +2 . I would imagine you have N values in intervals and therefore when i >= (N/2) you get an overflow.

Try this:

for(i = 0; i < N; i++)
{
    minuteunit[2*i] = new Tuple(intervals.get(i).getBeginMinuteUnit(),"s");
    minuteunit[2*i+1] = new Tuple(intervals.get(i).getEndMinuteUnit(),"e");
}

Also, assuming intervals should contain N entries, you could update your intervals.isEmpty() check to:

if(intevals.size() == N)
{
    ...

Answer 2

for(i = 0; i < ((2*N)-1); i = 1+2)

At each iteration i equals 3, so it never finishes. I think you want to add 2 at each iteration so use:

for(i = 0; i < ((2*N)-1); i = i+2)

Answer 3

You need to make your loop's termination condition i<2*N-2 , otherwise the iteration of adding 2 will push i over the end of your array when i is 2*N-2 (which it wi eventually be).

btw, I assume that your iteration of i=1+2 is a typo, and you have actually coded i=i+2

Answer 4

I'm going to take a shot in the dark here and guess that maybe intervals.get(i) is what's actually causing your problem here and not the array itself. Ignoring what appears to be a typo in the increment, the condition for your loop seems to be fine, since if i < 2*N - 1 , then i + 1 < 2*N and so there's no out of bound index for the array . That leaves the intervals.get(i) method.