Sunday , 16 December 2018
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Swapping two Strings without using third variable

This is the Java programming code written in BlueJ which swaps the values of two Strings without using any third (temp) variable.

Programming Code:

 * The class Swap_Strings takes 2 Strings as input and swaps their value without using any 3rd variable
 * @author :
 * @Program Type : BlueJ Program - Java

class Swap_Strings
    public static void main(String args[])throws IOException
        BufferedReader br=new BufferedReader (new InputStreamReader (;
        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("Strings Before Swapping : ");
        System.out.println("1st String = "+s1);
        System.out.println("2nd String = "+s2);

        /*Swapping Process Begins*/
        /*Swapping Process Ends*/

        System.out.println("Strings After Swapping : ");
        System.out.println("1st String = "+s1);
        System.out.println("2nd String = "+s2);


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


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]

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One comment

  1. This site is very useful for 10th class students .Do publish more programs for practice.Thanks you arouse my confidience in writing programs

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