Swapping Pairs of Characters in a String in Java
Last Updated :
20 Feb, 2024
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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: aJavExplanation: The given string contains even number of characters. Therefore, we swap every pair of characters.
Input: str = “GeeksForGeeks”
Output: eGkeFsroeGkesExplanation: 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.
// 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));
}
}
Output
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.
// 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));
}
}
Output
eGkeFsroeGkes
