Internal divided into categories: static inner classes, static inner classes of non-
member inner class is a member of the outer class, you can call an external class members.
How to use the outer member inner classes Class: class object to create
wai.nei wn = new wai () new nei ();.
Partial inner classes: internal class can access the class members
singletons:
constructor private
internal interface definition: double = 3.14 PI;
the Java wrapper classes provide for the corresponding eight basic data types
Java is a collection of a container for varying the number of stored objects, and realize common operations and algorithms in accordance with specifications. When programmers using Java collection class, without regard to the specific data structures and algorithms implementation details. The method requires the direct use of these collections and can call response, thereby improving development efficiency.
Java collection class are some common data structures, for example: queues, stacks, linked lists.
All Java collection classes in Java.util package List is sub-interface collection interface, you can use all the methods collection interface, since the list is ordered, repeatable set of interfaces so the list has added a number of the index the method of operation set of elements.
set a similar collection jar, multiple elements can be thrown into the jar, but can not remember the order of addition elements.