/*

 * A java program to swap strings without using the third variable.

 */

public class SwapStrings {

    public static void main(String[] args) {

        String firstString = "one";

        String secondString = "two";

        System.out.println("Before swapping....");

        System.out.println("The first String  = " + firstString);

        System.out.println("The second String = " + secondString);

        firstString = firstString + secondString; // step 1

        secondString = firstString.substring(0, (firstString.length() - secondString.length())); // step 2

        firstString = firstString.substring(secondString.length()); // step 3

        System.out.println("\nAfter swapping....");

        System.out.println("The first String  = " + firstString);

        System.out.println("The second String = " + secondString);

    }

}

​