Question

I am reading a tutorial regarding a Java pacman game.

Here is the code in question.

   if (pacmanx % blocksize == 0 && pacmany % blocksize == 0) {
        pos = // integer         
        ch = screendata[pos];

        if ((ch & 16) != 0) { // do not understand this.
            screendata[pos] = (short)(ch & 15);
            ...
        }

I am not really understanding the single &. I understand this operand checks both sides of an if statement, or is a bitwise operator. However, per the tests below, it doesn’t seem to be either:

if I was to test (ch = 18):
(ch & 16) = 16
(ch & 8) = 0
(ch & 2) = 2

thanks

Answer 1

& is the bitwise operator AND:

18 = 10010
16 = 10000
----------
16 = 10000


18 = 10010
 8 = 01000
----------
 0 = 00000

So the if will check if the fifth bit is 1 or 0.