Question

Say I have an ArrayList containing the elements {1,2,3,4}, and I want to enumerate all possible combinations of two elements in the ArrayList. i.e. (1,2), (1,3), (1,4), (2,3), (2,4), (3,4). What is the most elegant way of going about doing this?

Answer 1

Nested for loops would work:

for (int i = 0; i < arrayList.size(); ++i) {
    for (int j = i + 1; j < arrayList.size(); ++j) {
        // Use arrayList.get(i) and arrayList.get(j).
    }
}