Binary logarithm without java.lang.Math? -

i have 1 question, how posible perform binary logarithm without using math. have math.log(x)/math.log(2) , works can't use java.lang.math.

what can do?

int bits_necessaris = (int)(log2(nat+1)); //this correct  //the function hhave troubles, don't know :(  public static int log2(int x) {     return (something); } 

important: when performed math.log(7)/math.log(2) got 2.80xxxxx

so did :

(int) math.ceil(math.log(7)/math.log(2)); 

and 2.80xxxxx rounded got 3

the return of function has rounded up, example if solution 6,777 return has 7

you want know how many bits necessary represent int? then, there easier solutions, such as:

int bitsneededfor(int i) {     int bits = 0;     while (i > 0) {         bits++;         /= 2;     }     return bits; } 

on second thought, following faster , easier understand:

int bisneededfor(int i) {     return 32 - integer.numberofleadingzeros(i); }