1.java basic features of object-oriented: encapsulation, polymorphism and inheritance.
2.Java generic: iterator interface to the main hasnext () method, next () method, remove () method; collection interface inherits the iterator interface.
Then set the interface inherited the collection interface elements set of storage interfaces can not be duplicated, a repeat count. Wherein the interface implementation class are set Hashset ( element disorder, i.e., independent of order of the Add method () ), as well as the implementation class a LinkedHashSet ( ordered, i.e., related to () methods in the order the Add )
Then list interface is also inherited the collection interfaces, list elements stored in the interface can be repeated, is ordered . Wherein the interface implementation class list has ArrayList