Reversing string and toggle lower-upper-case

I need to write an application which takes a String as input. After processing, it should print out the string reversed, and all characters switched from lower to uppercase and vise versa. I want to achieve this using a StringBuilde开发者_开发技巧r.

Sample run:

Input: Hello Human

Output: NAMUh OLLEh

Here is a straight forward and simple way of solving the problem:

1. Read user input using for instance the Scanner class. and the nextLine() method. (Construct the Scanner by giving it System.in as argument.)

2. Create a StringBuilder.

3. Fetch the array of characters from the input string, using for instance input.toCharArray()

4. Reverse the array with Arrays.asList and Collections.reverse

   Collections.reverse(Arrays.asList(yourCharArray));
   

5. Loop through the list using for instance a for-each loop.

   for (Character c : yourCharArray) {
       ...
   }
   

6. For each character, check if c.isUpperCase (if so append c.toLowerCase()) else append c.toUpperCase().

(An alternative approach would be to give the StringBuilder the input-string as argument, and manipulate the string in-place using the reverse, charAt and setCharAt methods.)

To reverse a String use String reverse = new StringBuffer(YourString).reverse().toString();

Take a look at StringBuilder.reverse and Character.toLowerCase/Character.toUpperCase

Here's an "elite" 3-line solution:

    StringBuffer buffy = new StringBuffer("!GNIzA Ma").reverse();
    for (int i = 0; i < buffy.length(); i++)
        buffy.setCharAt(i, Character.isLetter(buffy.charAt(i)) ? (char) (buffy.charAt(i) ^ 32) : buffy.charAt(i));

    System.out.println(buffy); // "Am aZing!"

This works because the xor ^ with 32 (or 0x20) toggles the 3rd bit of the byte which changes upper to lower and visa versa. This toggling only works for letters of course.

      `function toggleCase(text){
         let toggledString='';
         for(let i=0;i<text.length;i++){
            if(text[i]==text[i].toUpperCase())
               toggledString+=text[i].toLowerCase();
            else if(text[i]==text[i].toLowerCase())
                    toggledString+=text[i].toUpperCase();
           }
         return toggledString;
       }`