JAVA Bitwise code purpose , &

Question

// following code prints out Letters aA bB cC dD eE ....

class UpCase {
public static void main(String args[]) {
 char ch;

 for(int i = 0; i < 10; i++) {
  ch = (ch         


        

Answer 1

Second piece of code(Showbits):

The code is actually converting decimal to binary. The algorithm uses some bit magic, mainly the AND(&) operator.

Consider the number 123 = 01111011 and 128 = 10000000. When we AND them together, we get 0 or a non-zero number depending whether the 1 in 128 is AND-ed with a 1 or a 0.

  10000000
& 01111011
----------
  00000000

In this case, the answer is a 0 and we have the first bit as 0. Moving forward, we take 64 = 01000000 and, AND it with 123. Notice the shift of the 1 rightwards.

  01000000
& 01111011
----------
  01000000

AND-ing with 123 produces a non-zero number this time, and the second bit is 1. This procedure is repeated.

First piece of code(UpCase):

Here 65503 is the negation of 32.

 32 = 0000 0000 0010 0000
~32 = 1111 1111 1101 1111

Essentially, we subtract a value of 32 from the lowercase letter by AND-ing with the negation of 32. As we know, subtracting 32 from a lowercase ASCII value character converts it to uppercase.