Swapping two Strings without using third variable

import java.io.*;

class Swap_Strings

{

    public static void main(String args[])throws IOException

    {

        BufferedReader br=new BufferedReader (new InputStreamReader (System.in));

        System.out.print("Enter the 1st String : ");

        String s1=br.readLine();

        int len1=s1.length();

 

        System.out.print("Enter the 2nd String : ");

        String s2=br.readLine();

 

        System.out.println("-------------------------------");

        System.out.println("Strings Before Swapping : ");

        System.out.println("1st String = "+s1);

        System.out.println("2nd String = "+s2);

 

        /*Swapping Process Begins*/

        s1=s1+s2;

        s2=s1.substring(0,len1);

        s1=s1.substring(len1);

        /*Swapping Process Ends*/

 

        System.out.println("-------------------------------");

        System.out.println("Strings After Swapping : ");

        System.out.println("1st String = "+s1);

        System.out.println("2nd String = "+s2);

    }

}




Output:

Enter the 1st String : Java For
Enter the 2nd String : School is Fun
——————————-
Strings Before Swapping :
1st String = Java For
2nd String = School is Fun
——————————-
Strings After Swapping :
1st String = School is Fun
2nd String = Java For

Working:

Initially s1 = “Java For” and s2 = “School is Fun”,
Now, the variable, ‘len1’ stores the length of the 1st String. Hence, in this case, ‘len1’ = 8

Step 1: s1 = s1+s2; gives s1 = “Java For”+”School is Fun”;
i.e. s1 = “Java ForSchool is Fun” [Note: There will be no space when we join the 1st and the 2nd String]

Step 2: s2=s1.substring(0,len1); gives, s2=”Java ForSchool is Fun”.substring(0,8);
i.e. s2 = “Java For”

Step 3: s1 = s1.substring(len1); gives, s1 = “Java ForSchool is Fun.substring(8);
i.e. s1 = “School is Fun”

Hence, finally we have s1 = “School is Fun” and s2 = “Java For”. [Swapping Done]