Все правильно
package com.javarush.task.task39.task3910;
/*
isPowerOfThree
*/
public class Solution {
public static void main(String[] args) {
System.out.println(isPowerOfThree(0));
}
public static boolean isPowerOfThree(int n) {
double c = n;
while(true){
c /=3;
if(c<2){break;}
}
return c==1;
}
}