Problem of overflow with lambda

Issue

I was using Lambda to sort order of elements going into my priority queue.

PriorityQueue<int[]> pq = new PriorityQueue<>((a, b) -> a[2] - b[2]);

While it will work perfectly fine in most cases, it can cause overflow issue.

It should return positive number if a[2] > b[2], but if a[2] - b[2] > Integer.MAX_VALUE, then might overflow exist.

For example: a[2] = Integer.MAX_VALUE, b[2] = -2, then a[2] - b[2] < 0

Solution

Well consider this overflow issue and implemnt the logic to prevent it

PriorityQueue<int[]> pq = new PriorityQueue<>((a, b) -> a[2] < b[2] ? -1 : a[2] == b[2] ? 0 : 1);

Or more simply, Integer.compareTo will solve this problem.

(a, b) -> (Integer.compare(a[0], b[0]))