[LeetCode]--342. Power of Four

Given an integer (signed 32 bits), write a function to check whether it is a power of 4.

Example:
Given num = 16, return true. Given num = 5, return false.

Follow up: Could you solve it without loops/recursion?

Credits:
Special thanks to @yukuairoy for adding this problem and creating all test cases.

Java Math的floor，round，ceil函数小结

跟上面的题一样，只不过换成了四。

public class Solution {
   
   
    private static