Question

I am looking some part of code that is supposed to get a single bit from an int.
It is as follows:

private int getBit( int token, int pos){  
   return ( token & ( 1 << pos ) ) != 0 ? 1 : 0;   
}

My question is why doesn’t it do it the following (simpler) way?

return token & ( 1 << pos );   

I expect that it will also return a 0 or 1.
Am I wrong on this? Is the second (mine) version wrong?

Answer 1

Your version is wrong. When you execute

return token & ( 1 << pos );

if it is non-zero, then you get an int with every bit except the pos bit zeroed out, because that is the number on the right side of the & operator. This obviously would only be 1 if pos==0.

This happens because the & operator simply takes the bitwise and operation between corresponding bits in the two ints. Since 1 << pos has a 1 bit in a position besides the lowest and token can presumably be any int, the result can also have a 1 bit in a position other than the lowest, making it greater than 1.