Permutations of Given Length in Java (Time Complexity: O(N!))

Given a non-negative integer N return the number of permutations of length N

Example:

Input: N = 3
Output: 6
Explanation: [
    [1, 2, 3],
    [1, 3, 2],
    [2, 1, 3],
    [2, 3, 1],
    [3, 1, 2],
    [3, 2, 1]
]