Java Bit Operation on Long - Counting Set and Unset bits

Question

I have a long number. Now what I want is following (given in pseudo code) ,

int cnt1 = 0 
int cnt2 = 0 

for each two bits of that long

       if the two bi         


        

Answer 1

What you need to do is keep shifting by 2 bits to the right at every iteration and do a bitwise and (&) operation with the number 3 (11 in binary):

long number;
int cnt1 = 0;
int cnt2 = 0;
long test = 3;
int counter = 0;    

while(counter < 64) { // we have 64 bits to inspect
    if((number & test) == 3) { // last 2 bits are 11
        cnt1++;
    } else { // last 2 bits are either 10, 01 or 00
        cnt2++;
    }          
    counter += 2;
    number = number >>> 2; // shift by 2 bits to the right
}