method swap to the Pair class of that swaps the first and second elements value of the pair in generic Pair class in java
public class Pair<T>
    {
       private T first;
       private T second;
   public Pair(T firstElement, T secondElement)
   {
      first = firstElement;
      second = secondElement;
   }
   public T getFirst() { return first; }
   public T getSecond() { return second; }
  public void swap()
  {
   T temp = first;
    first = second;
    second = temp;
  }
   public String toString() { return "(" + first + ", " + second + ")"; }
}
