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Welcome to the CSDN-markdown editor

java notes 1

1. virtual machine running.Class process

1 load classloader

2 check bytecodeverifer

3 execute runtime interpreter

  1. ctrl+s saves

    Ctrl+shift+F=ctrl+a +ctrl +i

    Alt+/ complete


    Windows+D returns desktop

    Windows+R opens and runs

    Windows+D turns on the computer

    Windows+L computer lock screen

    Ctrl+s saves

    Ctrl+c copy

    Select ctrl+a

    Ctrl+v paste

    Ctrl+z revoke

    Ctrl+o opens


  2. package declaration package and import boot package


4.Dos command d: switch drive

Dir lists the folder directory

CD enters folder cd.., back to upper level folder, cd/ CD, and back to root directory

Exit Dos CLS del from the screen to delete the file

5.JDK:Java development tools, including JRE;

JRE: Java running environment, including virtual machine and Java program class library

6. looks for the Java JDK bin directory location, opens the advanced system settings in the computer properties, and selects the environment variable,

Storage location; the new variable name JAVA_HOME; the variable value paste the JDK location; selects the Path variable name,

Enter%QQ-HOME% in the variable value; determine

7. annotation function: explanation, debugging error,

Classification: comment / multi line comment / / documentation comments /* */

8. keyword, lowercase


9. identifier is a character
that is used when a class, interface, method, or variable names are used
Composition: case characters, numbers, $

Note: you can't start with numbers, not Java keywords, case sensitive,

Rule name: package: folder

Name the package: all lowercase, domain name inversion, www.itheima.com, com.itheima., function word

Interface: class naming a word, the first letter is large, whether it's a single word or a number of

Methods and variables: one word is all lowercase, more than one word, starting from the second, uppercase,

Constants: one word is all capitalized, and many words are capitalized, but each word is underlined by

10. process oriented programming primarily requires solving problems based on the computer architecture

Process oriented programming allows you to describe problems based on problems,

11. a class is actually a data type

12. object oriented programming challenges the creation of a one to one mapping of objects in problem spaces, spaces, and


13. interface determines the requests that can be sent to a particular object

14. cohesion is the basic quality requirements of the program design, each refers to a software component in a function of the combination is very good, each object has a set of services it offers cohesion, in good object-oriented design, each object is able to complete a task but, don't try to do more.

The goal of the

15. client programmer is to collect various classes for rapid development, and the object of the class creator is to build the class

16. first considers the combination

when creating a new class
There are two ways in which

17. makes the base class and the inherited class differ by

1. directly add new methods to the inheritance class

2. change the existing base class, that is, to cover

18. single inheritance structure, c++ is not, there are three benefits,

1. all objects have a common interface,

2. all objects have certain functions,

3. make the garbage collector much easier to implement,