Why does one loop throw a ConcurrentModificationException, while the other doesn't?

Question

I\'ve run into this while writing a Traveling Salesman program. For an inner loop, I tried a

for(Point x:ArrayList) {
// modify the iterator
}         


        

Answer 1

You cannot modify a List while you are iterating over it which you are doing in the first example. In the second you simply have a regular for loop.