Since the Size of the list is 6, so indexes are 0,1,2,3,4,5 (which is value of i in this case)
You are always increasing the value of i by 1 and when it is i = 5, it is throwing IndexOutOfBoundsException.
As a fix you can do
if (i < 5 && current.equals(listaTags.get(i + 1))) {...}