⚽ Live Match: java/swapping pairs of characters in a string in java

Given a string, the task is to swap every two adjacent characters. If the string contains an odd number of characters, the last character remains unchanged.

The task is to swap every pair of adjacent characters in a string.
If the string has an odd length, the last character remains unchanged.

Examples:

Input: str = “Java”
Output: aJav
Input: str = “GeeksForGeeks”
Output: eGkeFsroeGkes

Approches to Swap Pairs of Char acters in a String

The problem can be solved using the following approaches:

1. Using String.toCharArray()

Convert the string into a character array.
Traverse the array in steps of 2.
Swap the current character with the next character.
If the length is odd, the last character is automatically left unchanged.
Convert the character array back to a string.

Java

public class GFG {

    // Method to swap adjacent character pairs
    static String swapPairs(String str) {

        // Handle null or empty string
        if (str == null || str.isEmpty()) {
            return str;
        }

        // Convert String to character array
        char[] chars = str.toCharArray();

        // Swap characters in pairs
        for (int i = 0; i + 1 < chars.length; i += 2) {

            char temp = chars[i];
            chars[i] = chars[i + 1];
            chars[i + 1] = temp;
        }

        // Convert character array back to String
        return new String(chars);
    }

    public static void main(String[] args) {

        String str = "GeeksForGeeks";

        System.out.println("Original String: " + str);
        System.out.println("Modified String: " + swapPairs(str));
    }
}

Output

Original String: GeeksForGeeks
Modified String: eGkeFsroeGkes

Explanation:

toCharArray() converts the string into a mutable character array.
i += 2 moves to the next pair of characters.
chars[i] and chars[i + 1] are exchanged using a temporary variable.
The condition i + 1 < chars.length prevents accessing an index outside the array.
For an odd-length string, the last character is not swapped.
new String(chars) creates the final string.

2. Using StringBuffer.append() Method

Traverse the string in pairs.
Append the second character followed by the first character.
If the string has an odd length, append the last character separately.
Convert the StringBuffer into a String.