Swap two Strings without using third user defined variable in Java

Ans:

Given two string variables a and b, swap these variables without using temporary or third variable in Java. Use of library methods is allowed.

Examples:

Input: a = "Hello"
       b = "World"

Output:

Strings before swap: a = Hello and b = World
Strings after swap: a = World and b = Hello

Solution Algorithm:

1) Append second string to first string and
   store in first string:
   a = a + b

2) call the method substring(int beginindex, int endindex)
   by passing beginindex as 0 and endindex as,
      a.length() - b.length():
   b = substring(0,a.length()-b.length());

3) call the method substring(int beginindex) by passing
   b.length() as argument to store the value of initial
   b string in a
   a = substring(b.length());
 
   
 Sample Code:

import java.util.*;

class SwapTest
{
public static void main(String args[])
{
String a = "Hello";
String b = "World";

System.out.println("Strings before swap: a = " + a + " and b = "+b);
a = a + b;
b = a.substring(0,a.length()-b.length());
a = a.substring(b.length());
System.out.println("Strings after swap: a = " + a + " and b = " + b);
}
}

Output:

Strings before swap: a = Hello and b = World
Strings after swap: a = World and b = Hello