TopK

public static int topK(int[] arr, int k) {
    if (arr == null || k > arr.length || arr.length == 0 || k <= 0) {
        return -1;
    }
    PriorityQueue<Integer> queue = new PriorityQueue<>(k, Comparator.reverseOrder());
    for (int i = 0; i < k; i++) {
        queue.add(arr[i]);
    }
    for (int i = k; i < arr.length; i++) {
        if (queue.peek() > arr[i]) {
            queue.poll();
            queue.add(arr[i]);
        }
    }
    return queue.peek();
}