NextGreaterElement.java

class Solution{
    public static long[] nextLargerElement(long[] arr, int n) { 
        Stack<Integer> stack = new Stack<>();
        stack.push(0);
        long[] result = new long[n];
        Arrays.fill(result, -1);
        for (int i = 1; i < n; ++i) {
            while (!stack.isEmpty() && arr[i] > arr[stack.peek()]) {
                result[stack.pop()] = arr[i];
            }
            stack.push(i);
        }
        return result;
    } 
}