Write a program in java input two string swapping two strings without using third variable.

Code:
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]