please explain the reason behind the output of this code

[Tarun wadhwa]

class Test{

	public static void main(String[] args){

		char ch = 'a';
		char bh = 'd';
		System.out.println((char)(ch + 'b'));
		char rs = (char) (ch + bh);
		System.out.println(rs);
		rs = (char) (ch-bh);
		System.out.println(rs);
		rs = (char) (ch*bh);
		System.out.println(rs);
		rs = (char) (ch/bh);
		System.out.println(rs);
	}
}

Output is:

macs-macbook:desktop mac$ javac Test.java
macs-macbook:desktop mac$ java Test
?
?
?
?

(after 4 ?'s there is a space shown for division operation by JVM)

[fred rosenberger]

characters are really integer values. You can add them together. If you look at an ascii chart, you'll see that 'a' is equal to 97, and 'b' is 98. so when you add ch + 'b', you effectively have 97 + 98, or 195.

When you then try and print this, it is outside the normal printable range, so you can get something weird.

[Tarun wadhwa]

The same Code mentioned above, if i run on windows platform it prints distinct special characters may i know the reason behind and with a detail explaination

[Sridhar Santhanakrishnan]

Not sure as I have never worked on a Mac, but maybe it tries to print using the extended apple table instead of unicode.

[Rob Spoor]

The console (cmd.exe on Windows, bash / csh / ... on Linux) is very limited in the characters it can display. Use JOptionPane to show the chars will be more informative, although it still can't display all characters:

class Test{   
   
    public static void main(String[] args){   
   
        char ch = 'a';   
        char bh = 'd';   
        JOptionPane.showMessageDialog(null, String.valueOf((char)(ch + 'b')));   
        char rs = (char) (ch + bh);   
        JOptionPane.showMessageDialog(null, String.valueOf(rs));   
        rs = (char) (ch-bh);   
        JOptionPane.showMessageDialog(null, String.valueOf(rs));   
        rs = (char) (ch*bh);   
        JOptionPane.showMessageDialog(null, String.valueOf(rs));   
        rs = (char) (ch/bh);   
        JOptionPane.showMessageDialog(null, String.valueOf(rs));   
    }   
}

[Campbell Ritchie]

You will have to follow Fred's suggestion of getting an ASCII chart, or a basic Unicode chart, which has the same values. Add the two chars together (remembering Unicode gives their values in hexadecimal, so use the hex option on your computer's calculator), and compare them with the ASCII values or the "extended" Unicode chart. Then you can see what the sum is supposed to mean. If you go beyond those two charts, the Unicode site will give lots more characters.
Remember that the DOS and Windows® command lines only have a restricted range of characters they can display, so even something like £ comes out as ú on it. And many characters simply come out as boxes or ?

[Tarun wadhwa]

Thanks to all of you your reply's helped me for the better understanding of my problem.