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.

public class Solution {
    public boolean isPowerOfFour(int num) {

        return num != 0 && (num & (num-1)) == 0 && (num & 0xAAAAAAAA) == 0;

    }
}