arraylist

PT_

heey, i want to 'delete' my arraylist, to clear it i've this but that doesn't work:

for (int i = 0; i < x_waarden.size(); i ++) {
        x_waarden.remove(0);
        y_waarden.remove(0);
}

i've 2 arraylists, x_waarden and y_waarden, both the same size

Mikeshiny

Hey, I haven't really looked at why your code is wrong, but I just recently had to do the same thing in one of my projects. Here is the code I used to empty out an arraylist:

for(int i = tryPattern.size()-1; i > -1; i--)
{
  tryPattern.remove(i);
}

So I start from the end and work my way down. Hope this helps!

~Mikeshiny

koogs

ArrayList has a clear() method:

http://docs.oracle.com/javase/7/docs/api/java/util/ArrayList.html

void clear() Removes all of the elements from this list.

GoToLoop

Method clear() got the added benefit of avoiding redundant instantiations and spare the GC! :-j

KevinWorkman

GoToLoop is correct, ArrayList has a clear() method that you should probably use. Alternatively, you could just reinitialize the ArrayList.

The reason your code doesn't work is the way you're looping. Try printing out the value of i and the current size of the ArrayList every iteration of the loop.

Let's say your ArrayList starts out at size 3. During the first iteration, i is 0 and size is 3. Second iteration, i is 1 and size is 2. Third, i is 2 and size is 1. Uh oh, i is greater than size, so your loop exits, and your ArrayList is not completely cleared.