Why char 0 + short 9 = 57 ?

Question sur la mission

Mission n°4 sur les conversions des types d'entiers

Résolues

Hello, I've found the answer but I don't understand why: - When I print nombre, I get: 9 - When I print zero, I get 0 But when I add each other, I get: 57 ??, why?

public class Solution {
    public static void main(String[] args) {
        short nombre = 9;
        // System.out.println(nombre); 			= 9
        char zero = '0';
        // System.out.println(zero); 			= 0
        // System.out.println(zero + nombre);	= 57??
    }
}

Thanks ! 😁

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Guadalupe Gagnon

niveau Tampa, Tampa, United States

6 avril 2022, 14:04

solution

See this link to the ASCII table. The char '0' is stored as the number 48. Whenever you perform mathematical operations on chars they are first converted to integers. Therefore when you add the variables 'zero' and 'nombre' the computer will add 48 to 9 and arrive at the answer of 57. If you look at the ASCII table the number 57 is what the char '9' is stored as. You can cast the result of the addition to a char before it prints to the screen to get the output 9 simply like this:

System.out.println((char)(zero + nombre)); // outputs 9

Guadalupe Gagnon

niveau Tampa, Tampa, United States

6 avril 2022, 14:09

Another quick example, if we change the data type of 'nombre' to char instead of int and try the code the output of the line where they are added together will change:

public static void main(String[] args) {
   char nombre = '9';
   System.out.println(nombre); // outputs 9
   char zero = '0';
   System.out.println(zero); // outputs 0
   System.out.println(zero + nombre); // outputs 105
}

It now outputs 105. This is because char's are numbers and when mathematical operations are applied to them they are cast as int's to do the operation. The char 0 is 48 and the char 9 is the number 57. When adding 48 and 57 you end up with 105. Because char's are numbers you can use them as exactly like numbers. Take this example:

for(int i = 'a'; i <= 'z'; i++) // int
   System.out.println(i);

This outputs the numbers 97 - 122.

for(char i = 'a'; i <= 'z'; i++) // char
   System.out.println(i);

While this, by simply changing the loop variable from 'int' to 'char', outputs the lowercase letters of the alphabet.

Anonymous #10962800

, Switzerland

12 avril 2022, 15:43

Thanks a lot !😄😀😀