每天一道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?

public class Solution {
public boolean isPowerOfFour(int num) {
int n=num;
while(n>0&&n%4==0){
n/=4;
}
return n==1;
//return (num > 0) && ((num & (num - 1)) == 0) && ((num & 0x55555555) == num);
}
}