How to check if an integer can be divided by 3

Question

How to check if my integer can be divided by 3 as below:

for(int i=0; i<24;  i++){
   //here, how to check if \"i\" can be divided by 3 completely(e.g. 3,         


        

Answer 1

Well, what you could do (it might be a bit faster; it is faster on my machine) is:

boolean canBeDevidedBy3 = ((int) (i * 0x55555556L >> 30) & 3) == 0;

instead of

boolean canBeDevidedBy3 = (i % 3) == 0;

However, the multiplication trick only works for -2 <= i <= 1610612735. This answer was inspired by this optimization question. But if I can give you a tip: use (i % 3) == 0. It's so much simpler, and will always work.