Java program to swap first and last characters of words in a sentence

Problem Statement

Given a sentence, create a  program in Java that swaps the first and last characters of each word efficiently as given below ?

Input

That is a sample

Output

The string after swapping the last characters of every word is :
thaT si a eampls

Steps to swap first and last characters of words in a sentence

Below are the steps to swap first and last characters of words in a sentence ?

• Convert string to character array.
• Iterate through the character array using while loop to identify the beginning and end of each word.
• For each word, swap the first and last characters.
• Convert the modified character array back into a string and return it.

Java program to swap first and last characters of words in a sentence

public class Demo {
 static String swap_chars(String my_str) {
char[] my_ch = my_str.toCharArray();
for (int i = 0; i < my_ch.length; i++) {
 int k = i;
 while (i < my_ch.length && my_ch[i] != ' ')
i++;
char temp = my_ch[k];
my_ch[k] = my_ch[i - 1];
my_ch[i - 1] = temp;
}
return new String(my_ch);
 }
 public static void main(String[] args) {
String my_str = "That is a sample";
System.out.println("The string after swapping the last characters of every word is : ");
System.out.println(swap_chars(my_str));
 }
}

Output

The string after swapping the last characters of every word is :
thaT si a eampls

Code explanation

The Demo class contains a method called swap_chars() that returns a string. In this method, the input string my_str is converted to a character array my_ch using the toCharArray() method. A for loop iterates over the character array my_ch using its length, my_ch.length. Within the loop, an integer k stores the current index. A while loop then iterates as long as i is less than my_ch.length and my_ch[i] is not a space. For each word, if the next character is not a space, it swaps the first and last characters.

After processing all words, the modified character array is converted back to a string and returned. In the main method, the string my_str is defined, and the swap_chars() method is called with this string as a parameter. The result is then printed to the console.