Program to Replace Lower-Case Characters with Upper-Case and Vice Versa

Q. Program to replace lower-case characters with upper-case and vice versa.

Here, our task is to replace all the lower-case characters in the string to upper-case and upper-case characters to lower-case. For this purpose, we need to traverse the string and check for each character. If the character is a lower-case character, make it upper-case by using the language-specific built-in method or add 32 to the lower-case character in C to change the ASCII value of the character.

Algorithm

Define a string and traverse through it.
If the lower-case character is encountered then convert them in upper case character using built-in function.
If the upper-case character is encountered then convert them in upper case character using built-in function.
If it's a character other than upper-case or lower-case alphabet take the character as it is.

Solution

Python

str1="Great Power";
newStr = "";
 
for i in range(0, len(str1)):
    #Checks for lower case character
    if str1[i].islower():
        #Convert it into upper case using upper () function
        newStr += str1[i].upper();
    #Checks for upper case character
    elif str1[i].isupper():
        #Convert it into lower case using lower () function
        newStr += str1[i].lower();
    
    else:
        newStr += str1[i];        
print("String after case conversion : " +  newStr);

Output:

String after case conversion : gREAT pOWER

C

#include <stdio.h>
int main()
{
    int i, len = 0;
    char str[] = "Great Power";
    
    //Calculating length of the array
    len = sizeof(str)/sizeof(str[0]);
    
    //Checks every character in the array
    for(i = 0; i < len; i++){
        
        //Checks whether a character is upper case character
        if(isupper(str[i])){
            //Convert that charcter to lower case
            str[i] = tolower(str[i]);
        }
        //Checks whether a character is lower case character
        else if(islower(str[i])){
            //Convert that charcter to upper case
            str[i] = toupper(str[i]);
        }
    }
    printf("String after case conversion : %s", str);
    return 0;
}

Output:

String after case conversion : gREAT pOWER

JAVA

public class changeCase {
    public static void main(String[] args) {
        
        String str1="Great Power";
        StringBuffer newStr=new StringBuffer(str1);
        
        for(int i = 0; i < str1.length(); i++) {
            
            //Checks for lower case character
            if(Character.isLowerCase(str1.charAt(i))) {
                //Convert it into upper case using toUpperCase() function
                newStr.setCharAt(i, Character.toUpperCase(str1.charAt(i)));
            }
            //Checks for upper case character
            else if(Character.isUpperCase(str1.charAt(i))) {
                //Convert it into upper case using toLowerCase() function
                newStr.setCharAt(i, Character.toLowerCase(str1.charAt(i)));
            }
        }
        System.out.println("String after case conversion : " + newStr);
    }
}

Output:

String after case conversion : gREAT pOWER

C#

using System;
public class Program
{
    public static void Main()
    {
        string str1="Great Power";
        char ch;
        System.Text.StringBuilder str2 = new System.Text.StringBuilder();
 
        for(int i = 0; i < str1.Length; i++) {
            //Checks for lower case character
            if(char.IsLower(str1[i])) {
                //Convert it into upper case using ToUpper() function
                ch = Char.ToUpper(str1[i]);
                //Append that character to new character
                str2.Append(ch);
            }
            //Checks for lower case character
            else if(char.IsUpper(str1[i])) {
                //Convert it into lower case using ToLower() function
                ch = Char.ToLower(str1[i]);
                //Append that character to new character
                str2.Append(ch);
            }
            else{
                ch = str1[i];
                str2.Append(ch);
            }
        }
        Console.WriteLine("String after case conversion : " + str2);
    }
}

Output:

String after case conversion : gREAT pOWER

PHP

<!DOCTYPE html>
<html>
<body>
<?php
    $str1 = "Great Power";
    for($i = 0; $i < strlen($str1); $i++){
        //Checks for lower case character
        if($str1[$i] >= 'a' && $str1[$i] <= 'z'){
            //Convert it into upper case using strtoupper() function
            $str1[$i] = strtoupper($str1[$i]);
        }
        //Checks for lower case character
        elseif($str1[$i] >= 'A' && $str1[$i] <= 'Z'){
            //Convert it into upper case using strtolower() function
            $str1[$i] = strtolower($str1[$i]);
        }
    }
echo "String after case conversion : $str1";
?>
</body>
</html>

Output:

String after case conversion : gREAT pOWER

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