Create a new class Cell and do a unit test in bluej. The class has the following:

1. Val: a private variable - Integer

2. next: a private variable - Cell

3. Append( Integer x ): checks to see if next is null. If it is, create a new Cell and assign it to next, and set the value of val to x. Otherwise call append(x) on next. 4. toString(): returns a String constructed by pre-pending val to the String returned by applying toString() to next (if next is not null)