Add a method to Pair that implements the following description.

Question

```
/**
* Determine if either element of this Pair is equal
* to the argument.
* @param e the object to compare to the elements of this Pair
* @return the first element of this Pair found equal
* to e, null if neither element is equal to
* e.
*/
T elementEqualTo( T e )


```

Answer 1

```
/**
* Determine if either element of this Pair is equal
* to the argument.
* @param e the object to compare to the elements of this Pair
* @return the first element of this Pair found equal
* to e, null if neither element is equal to
* e.
*/
public T elementEqualTo (T e)
{
if ( e == null)
throw new NullPointerException();

if ( this.firstElement.equals( e ) || this.secondElement.equals( e ) )
return e;
else
return null;
}

```