int answer = 0;
if (sortIndex < 0 || sortIndex >= functions.size()) {
answer = compareDefaultSortColumn(e1, e2, sortIndex);
} else {
Function1 function = functions.get(sortIndex);
Object v1 = function.apply(e1);
Object v2 = function.apply(e2);
answer = Objects.compare(v1, v2);
if (answer == 0) {
answer = compareDefaultSortColumn(e1, e2, sortIndex);
}