1.Create an abstract class AListADT. The class will have the following methods (no constructors) declared with an empty body:

a. append( Integer x ): inserts x at the end of the list

b. toString(): returns a String that is stored in this list

c. isEmpty(): returns true if the list is empty.

2. Create a class AList that inherits from AListADT. The class has the following:

a. root: a private variable - Cell

b. append( Integer x ): checks to see if root is null. If it is, create a new Cell and assign it to root. Call append(x) on root.

c. toString(): checks to see if root is null. If it is, return the empty String. Otherwise, return the String from calling toString() on root.

d. isEmpty(): returns true if root is null. Otherwise return false.

There is a class Cell created, if that class is needed, please say it.