First,I dont want to tell me about abstract class,inherit each.Its just Stereo,Ygro,Aerio classes that starts like public class Stereo{//code inside } there arent ectended any c
EDITED:
Food[] pin = new Food[A];
This is an array of type Food. It can hold objects of type food and other types of food (pizza, corn, potato), which are extended from Food. If you did not extend your Stereo class from Food, for example, then you cannot store any instances of it in this array.
Look at this tutorial, or find another one on generic inheritance, to help you understand this concept.
http://self-learning-java-tutorial.blogspot.com/2014/03/generics-and-inheritance.html