How to get upper case instead of lower case in a string without method toUppercase. P.S below

Question

How to get upper case instead of lower case in a string without method toUppercase, but the other symbols should not change in the string

   package com.telukhin.hw6;

public class Task1 {
    public static void main(String[] args) {

    } private static String lowerCase(String s) {
        for (int i = 0; i < s.length(); i++) {
            char ch = s.charAt(i);
            if(ch >= 'a' && ch < 'z') {
                ch = ch - '32';
            }


        }
    }
}

Answer 1

You can do it as follows:

public class Task1 {
    public static void main(String[] args) {
        System.out.println(lowerCase("HELLO"));
    }

    private static String lowerCase(String s) {
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < s.length(); i++) {
            char ch = s.charAt(i);
            if (ch >= 65 && ch <= 90) 
                sb.append((char)(ch+32));           
            else
                sb.append((char)ch);
        }
        return sb.toString();
    }
}

Output:

hello

Please check https://www.cs.cmu.edu/~pattis/15-1XX/common/handouts/ascii.html for reference.

UPDATE: Adding a method to convert a String to upper case as well

public class Task1 {
    public static void main(String[] args) {
        System.out.println(lowerCase("HELLO"));
        System.out.println(upperCase("hello"));
    }

    private static String lowerCase(String s) {
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < s.length(); i++) {
            char ch = s.charAt(i);
            if (ch >= 65 && ch <= 90) //ASCII value of 'A'is 65 and that of 'Z' is 90
                sb.append((char)(ch+32));           
            else
                sb.append((char)ch);
        }
        return sb.toString();
    }
    private static String upperCase(String s) {
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < s.length(); i++) {
            char ch = s.charAt(i);
            if (ch >= 97 && ch <= 122) //ASCII value of 'a'is 97 and that of 'z' is 122
                sb.append((char)(ch-32));           
            else
                sb.append((char)ch);
        }
        return sb.toString();
    }
}

Output:

hello
HELLO