1面向对象与面向过程
2.OO的特点
(1)封装性
（2）继承性
（3）多态性
3.Class and Object
(1)define a class
(2)gloables and local variables
(3)constructor‘s defination and application
(4)create an object
declration an object
allocate memory
(5)use an object
use the member variables and change them
use the member function
use operator ‘.‘ to access the member variables and functions
(6)deallocate an object
java use the "Garbage collection "to deallocate the memory: first: estimate whether a variable is in use; second: deallocate
java also provide a function "finalize()" before "garbage collection" for "garbage collection system" (got hazed ,gcs is differ from gc?)
4.use packages
def:(1)in essence facilate the search and use of a specfic class
(2)there exists the cogniminal class, to some extent ,this can avoid the conflict of nominate
(3)in java the access right is measured in packages
create a package:
use classes in the same package and public classes in other packages:
(1)long names connected by dot
(2)use keyword ‘import‘:import pack.class|*