Toggle each character in a string in Java

Understanding Character Toggling

Character toggling means converting uppercase letters to lowercase and vice versa.

We will explore three different methods to toggle characters in a string using Java.

Method 1: Using a Loop

This method iterates through the string and toggles each character.

import java.util.Scanner;

public class ToggleCase {
    public static String toggleCase(String str) {
        StringBuilder result = new StringBuilder();
        for (char ch : str.toCharArray()) {
            if (Character.isLowerCase(ch))
                result.append(Character.toUpperCase(ch));
            else if (Character.isUpperCase(ch))
                result.append(Character.toLowerCase(ch));
            else
                result.append(ch);
        }
        return result.toString();
    }

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.print("Enter a string: ");
        String str = scanner.nextLine();
        System.out.println("Toggled string: " + toggleCase(str));
        scanner.close();
    }
}
            

Method 2: Using Recursion

This method toggles characters recursively.

import java.util.Scanner;

public class ToggleRecursive {
    public static String toggleRecursive(String str, int index) {
        if (index == str.length()) return "";
        char ch = str.charAt(index);
        char toggledChar = Character.isLowerCase(ch) ? Character.toUpperCase(ch) : Character.toLowerCase(ch);
        return toggledChar + toggleRecursive(str, index + 1);
    }

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.print("Enter a string: ");
        String str = scanner.nextLine();
        System.out.println("Toggled string: " + toggleRecursive(str, 0));
        scanner.close();
    }
}
            

Method 3: Using Character Array

This method toggles characters by modifying a character array.

import java.util.Scanner;

public class ToggleCharArray {
    public static String toggleCharArray(String str) {
        char[] charArray = str.toCharArray();
        for (int i = 0; i < charArray.length; i++) {
            charArray[i] ^= 32;
        }
        return new String(charArray);
    }

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.print("Enter a string: ");
        String str = scanner.nextLine();
        System.out.println("Toggled string: " + toggleCharArray(str));
        scanner.close();
    }
}