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) {          if(num<=0)              return false;          return (num & num-1)==0 && (num&0x55555555)==num;        }  }