Swapping Pairs of Characters in a String in Java

30 Aug, 2020
Given string str, the task is to write a Java program to swap the pairs of characters of a string. If the string contains an odd number of characters then the last character remains as it is.
Examples:
Input: str = “Java”
Output: aJva
Explanation: The given string contains even number of characters. Therefore, we swap every pair of characters.
Input: str = “GeeksForGeeks”
Output: eGkeFsroeGkes
Explanation: The given string contains odd number of characters. Therefore, we swap every pair of characters and last character remains as it is.
1. Using String.toCharArray() Method
Get the string to swap a pair of characters.Check if the string is null or empty then return the string.Converting the given string into a character array.Traverse the character array and swap the characters.Now, print the result.
Get the string to swap a pair of characters.
Check if the string is null or empty then return the string.
Converting the given string into a character array.
Traverse the character array and swap the characters.
Now, print the result.
Java
// Java program to swap pair// of characters of a string  class GFG {      // Function to swap pair of    // characters of a string    public static String swapPair(String str)    {          // Checking if string is null        // or empty then return str        if (str == null || str.isEmpty())            return str;          // Converting the given string        // into a character array        char[] ch = str.toCharArray();          // Traverse the character array        for (int i = 0; i < ch.length - 1; i += 2) {              // Swapping the characters            char temp = ch[i];            ch[i] = ch[i + 1];            ch[i + 1] = temp;        }          // Converting the result into a        // string and return        return new String(ch);    }      // Driver Code    public static void main(String args[])    {          // Given String str        String str = "GeeksForGeeks";          // Print the result        System.out.println(swapPair(str));    }}
eGkeFsroeGkes



2. Using StringBuffer.append() Method
Get the string to swap a pair of characters.Check if the string is null or empty then return the string.Creating a StringBuffer object with a length of the string passed as a parameter.Traverse the string and append the characters in the StringBuffer object in reverse order.Check if the string contains an odd number of characters then append the last character into the StringBuffer object.Now, print the result.
Get the string to swap a pair of characters.
Check if the string is null or empty then return the string.
Creating a StringBuffer object with a length of the string passed as a parameter.
Traverse the string and append the characters in the StringBuffer object in reverse order.
Check if the string contains an odd number of characters then append the last character into the StringBuffer object.
Now, print the result.
Java
// Java program to swap pair// of characters of a string  class GFG {      // Function to swap pair of    // characters of a string    public static String swapPairs(String str)    {          // Checking if string is null        // or empty then return str        if (str == null || str.isEmpty())            return str;          int len = str.length();          // Creating a StringBuffer object with        // length of the string passed as a parameter        StringBuffer sb = new StringBuffer(len);          // Traverse the string and append        // the character in the StringBuffer        // object in reverse order        for (int i = 0; i < len - 1; i += 2) {            sb.append(str.charAt(i + 1));            sb.append(str.charAt(i));        }          // Checking if the string has        // odd number of characters        // then append the last character        // into StringBuffer object        if (len % 2 != 0) {            sb.append(str.charAt(len - 1));        }          // Converting the StringBuffer        // into the string and return        return sb.toString();    }      // Driver Code    public static void main(String args[])    {          // Given String str        String str = "GeeksForGeeks";          // Print the result        System.out.println(swapPairs(str));    }}
eGkeFsroeGkes



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