LeetCode342. Power of Four

public class Solution {
public boolean isPowerOfFour(int num) {
if(num<=0){
return false;
}
String s = Integer.toBinaryString(num);//数字转二进制串,4的幂模式为“1{00}*”
s=s.substring(1);
if(s.indexOf("1")>=0){
return false;
}
if(s.length()%2==0){
return true;
}
return false;
}
}