Swapping case of a single alphabetical word

Rahul Verma :

I've found this code for swapping case, but I'm a bit confused on how it works.

class Main {
  private static String swapCase(String s) {
      String r = "";
      for (char c : s.toCharArray())
          r += c ^= 32; // this line
      return r;
  }

  public static void main(String[] args) {
    System.out.println(swapCase("Hello"));
  }
}

I understood that it loops over each character. But, I can't wrap my head around the line (especially the XOR operator)

r += c ^= 32; 

I mean what's the significance of 32. How it swaps the case.

Can somebody help me?

Eugene :

This is how ASCII was set-up.

Letter from a-z have the 6-th bit set to 1; while letters from A-Z have the 6-th bit set to 0.

32 = 100000 // the 6-th bit is set to 1

doing a XOR with an int will invert that 6-th bit.

You could do a little of debugging and see yourself:

for (char c : s.toCharArray()) {
        System.out.println(Integer.toBinaryString((int) c));
        c ^= 32; // this line
        System.out.println(Integer.toBinaryString((int) c));
}