Write a complete program with an abstract class Shape that holds the name, declares abstract double area(), and has a finished describe() using that area.
Add Square and Triangle subclasses supplying only area(). Read the square side, then the triangle base and height, and print the description of each.
For the input 3 4 6:
Square has area 9.0
Triangle has area 12.0
Note that describe() is written once in the abstract class, yet it calls each subclass's own area().