JAVA-DAY01, environment variable configuration

I. Basic computer knowledge (Computer overview) (understanding)

1 . What is a computer? Application examples of computer in life

A: computer (computer) Full name: Electronic computers, commonly known as computers. It is a modern intelligent electronic device which can operate according to the program, automatically and high-speed processing massive data. A computer consisting of hardware and software that does not have any software installed is called bare metal. Common forms are desktop computers, laptops, mainframe computers, and so on.

* Application Examples

* 1: Scientific calculation

* 2. Data processing

* 3, Automatic control

* 4. Computer Aided design

* 5, Artificial intelligence

* 6, multimedia applications

* 7. Computer network

* Wait

2. What is hardware? Examples of hardware

A: Computer hardware (computer Hardware) refers to a computer system consisting of electronic, mechanical and optoelectronic components, such as a variety of physical devices collectively. These physical devices constitute an organic whole to provide the material basis for the computer software operation according to the requirements of the system structure.

* von Neumann architecture

* The hardware of the computer is divided into 5 components: an operator, a controller, a memory, an input device, and an output device.

* Operators and controllers are the core of the computer, collectively referred to as central processing unit (processing UNIT,CPU) or processor. There are also some high-speed storage units inside the CPU, called registers. Where the operator performs all arithmetic and logic operations, the controller is responsible for removing the instruction from the memory, decoding and issuing various control commands to the computer, while the register provides the processing unit with the data required for operation.

* Memory is the memory part of a computer, used to store the program and the data involved in the program. It is divided into internal memory and external memory. The internal memory is used to store the program being executed and the data used, its cost is high, the capacity is small, but the speed is fast. External memory can be used for long-term preservation of a large number of programs and data, low cost, large capacity, but slower.

* Input devices and output devices are collectively referred to as external devices, referred to as peripheral or I/O devices, for human-computer interaction and inter-machine communication. Microcomputers commonly used in the input device has a keyboard, mouse, etc., the output device has a display, printer and so on.

3. What is software? Software classification and examples

A: Computer software (computer software) is an essential thing in the process of using a computer, computer software can make the computer in a predetermined order to complete the specific functions

* Computer software is divided into system software and application software according to its function.

* System software: DOS (Disk Operating system), Windows, Linux, Unix, Mac, Android, IOS

* Application software: Office QQ chat YY language minesweeper

II. Basic Computer knowledge (software development and Computer language Overview) (understanding)

* 1, what is software

* Collection of computer data and instructions organized in a specific order

* 2, what is development

* Process of software production

* 3, what is software development

* Build software with development tools and computer language

* 4, what is the computer language

* A special language for communication of information between people and computers

* 5, the classification of computer language

* Machine Language:

* Machine language is a computer language directly expressed as a binary code instruction, which is a string of code consisting of 0 and 1, which have a certain number of digits and are divided into segments, and the coding of each segment represents different meanings.

Assembly language

* Assembly language is the use of some special symbols to replace the machine language binary code, the computer can not directly recognize the need for a software to translate assembly language into machine languages.

* Advanced Language:

* The source code is written in plain English, and the source code is translated by the compiler into a machine language that is directly recognized by the computer and then executed by the computer.

* Advanced languages include C,c++,c#,java

Third, computer basic knowledge (man-machine Interaction) (understanding)

* 1, two ways of human-computer interaction

* A: Command line mode

* Need to have a console, enter specific instructions, let the computer do some operations. More trouble, need to record some commands.

* B: Graphical interface mode

* This method is simple and intuitive, the user is easy to accept, easy to operate.

Iv. Basic Computer Knowledge (keyboard function keys and shortcut keys) (master)

* 1, keyboard function keys

* A:tab

* B:shift

* C:ctrl

* D:alt

* E: space

* F:enter

* G:window

* H: up or down key

* I:PRTSC (Printscreen) screen

* 2, keyboard shortcuts (master)

* A:ctrl+a Select All

* B:ctrl+c Copy

* C:ctrl+v Paste

* D:ctrl+x Cut

* E:ctrl+z Revocation

* F:ctrl+s Save

v. BASIC Computer knowledge (how to open the DOS console) (master)

* 1, XP How to open the DOS console?

* A: Start--Program--Attachments--command prompt

* B: Start-run--cmd--Enter

* c:win+r--cmd--Enter

* 2, Win7 How to open the DOS console?

* A: Start-All Programs--attachments--command prompt

* B: Start-search programs and files--cmd--enter

* c:win+r--cmd--Enter

* 3, Win8 How to open the DOS console

* A: Left mouse click Start--down arrow--command prompt

* B: Mouse Right click Start--Search--cmd--Enter

* C: Mouse Right click Start-run--cmd--Enter

* d:win+r--cmd--Enter

VI. Basic Computer knowledge (Common DOS command explained)

* A:D: Enter drive letter Toggle

* B:dir (Directory): Lists the files and folders in the current directory

* C:CD (change directory) changes the specified directory (enter the specified directory)

* D:CD. : Back to the top level directory

* e:cd\: Go back to the root directory

* F:cls: (Clear screen) clear

* G:exit: Exit DOS command line (need to master on split Line, understand below)

* /=========================================================

* MD (make directory): Create directory

* RD (remove directory): Delete directory

* DEL (delete): Delete files, delete a bunch of suffix names like files *.txt

* Notepad Create File

* Delete a folder with content

* Rd +/S folder name (ask whether to delete)

* RD +/q +/S folder name (delete directly)

Vii. Java Language Foundation (Java language Overview) (Learn)

* 1. History of Java language

* James Goslin James Gosling received a BS in computer Science from the University of Calgary in 1977, a PhD in computer science from Carnegie Mellon University in 1983, and worked at IBM after graduating to design IBM's first generation workstation news system, but with no regard for attention. Later transferred to Sun, 1990, and Patrick,naughton and Mike Sheridan and other people to cooperate "Green plan", later developed a set of languages called "Oak", then renamed Java.

* SUN (Stanford University Network, Stanford University Internet company)

* 2, Java language version

* JDK 1.1.4 sparkler gem 1997-09-12

* JDK 1.1.5 Pumpkin Pumpkin 1997-12-13

* JDK 1.1.6 Abigail Abigail--Women's name 1998-04-24

* JDK 1.1.7 Brutus Brutus--Roman statesman and general 1998-09-28

* JDK 1.1.8 Chelsea Chelsea-city name 1999-04-08

* J2SE 1.2 Playground Sports Ground 1998-12-04

* J2SE 1.2.1 None No 1999-03-30

* J2SE 1.2.2 Cricket cricket 1999-07-08

* J2SE 1.3 Kestrel Americas Red Falcon (SǓN) 2000-05-08

* J2SE 1.3.1 Ladybird Ladybug 2001-05-17

* J2SE 1.4.0 Merlin grey back Falcon 2002-02-13

* J2SE 1.4.1 Grasshopper Grasshopper 2002-09-16

* J2SE 1.4.2 Mantis Mantis 2003-06-26

* Javase 5.0 (1.5.0) Tiger Tigers

* Javase 5.1 (1.5.1) Dragonfly Dragonfly

* Javase 6.0 (1.6.0) Mustang Mustang

* Javase 7.0 (1.7.0) Dolphin Dolphin

* 3. Java language Platform

* J2SE (Java 2 Platform standard Edition) edition

* is a solution for the development of common desktop and business applications, which is the basis of the other two, and can complete the development of some desktop applications

* J2ME (Java 2 Platform micro Edition) Mini version

* is a solution for the development of electronic consumer products and embedded devices

* EE (Java 2 Platform Enterprise Edition) Corporate Edition

* is a set of solutions for applications in developing enterprise environments, including technologies such as Servlets, JSPs, etc., primarily for web application development

* 4. Java language Features

* Simple Nature

* Explanatory nature

* Object Oriented

* High Performance

* Distributed processing

* Multithreading

* Robustness

* Dynamic

* Structural neutrality

* Security

* Open Source

* Cross-platform

Viii. Java Language Foundation (Java language Cross-platform principle) (master)

* A: What is cross-platform

* B:java Language Cross-platform principle

* Just install a Java Virtual machine (JVM Java VM) on the operating system that needs to run the Java application. The JVM is responsible for the operation of the Java program in the system.

* C:java language cross-platform illustration

* Write once, run anywhere! (one compile, run everywhere)

Ix. Java Language Foundation (Overview of JRE and JDK) (master)

* A: What is the JRE

* Including Java virtual machines (JVM Java) and Java programs required by the core class library, if you want to run a well-developed Java program, the computer only need to install the JRE.

* jre:jvm+ class Library.

* B: What is a JDK

* JDK is available to Java developers and includes Java development tools and JRE. So with the JDK installed, you don't have to install the JRE separately.

* Development tools: Compiler tool (Javac.exe) packaging Tool (Jar.exe), etc.

* Development tools for Jdk:jre+java.

* C: Why the JDK contains a JRE

* Why does the JDK contain a JRE?

* After the development of the program, you need to run a look at the effect.

* Role and relationship of D:JDK,JRE,JVM

X. Java language Foundation (download and installation process diagram for JDK) (learn)

* 1, download the JDK

* A: Official website http://www.oracle.com

* B: Demo download process

* 2, installation of JDK

* A: Fool-type installation

* Double click on the installer, then all the way next (but not recommended)

* B: Recommended way to install

* Installation path do not have Chinese or special symbols such as spaces.

* All development related software is best installed directory unified.

* Example: my JDK installation path

* 3, \develop\java\jdk1.7.0_72

* When prompted to install the JRE, you can choose not to install. Recommended or installed.

* C: Demo installation process

* You can set up a folder on the D drive first develop

* Then demonstrate the installation process

* 4, verify the installation is successful

* A: Through the DOS command, switch to the JDK installation bin directory.

* 5, \develop\java\jdk1.7.0_72\bin

* B: Then enter Javac and Java separately, if some content is displayed correctly, the installation is successful.

Xi. Java Language Foundation (directory interpretation under JDK installation path) (learn)

* A:bin Directory: This directory is used to store some executable programs.

* such as Javac.exe (Java compiler), Java.exe (Java Runtime Tool), Jar.exe (Packaging tool) and * Javadoc.exe (document Generation tool), etc.

* B:DB directory: DB directory is a small database.

* Starting with JDK 6.0, a new member javadb is referenced in Java, a pure Java implementation, open source database management system. This database is not only lightweight, but also supports all JDBC 4.0 specifications, when learning jdbc, no more need to install a database software, choose to use JAVADB directly.

* C:jre directory: "JRE" is the abbreviation for Java Runtime environment, meaning Java Program Runtime environment. This directory is the root of the Java Runtime Environment, which includes Java virtual machines, runtime class packages, Java application initiators, and a bin directory, but does not include development tools in the development environment.

* D:include directory: Because the JDK is implemented through C and C + +, you need to introduce some C-language header files at startup, which is used to store these header files.

* E:lib Directory: LIB is the abbreviation for the library, meaning the Java class library or library file, which is the archive package file used by the development tool.

* F:src.zip file: Src.zip is a compressed file for the SRC folder, and the source code of the JDK core class is placed in SRC, which allows you to view the source code of the Java base class.

12. Java Language Basics (Introduction to Java Development tools) (Learn)

* 1, Notepad (Microsoft operating system comes with)

* 2, editplus/notepad++

* 3. Eclipse

* 4, MyEclipse

* Give us a brief introduction to these tools and then tell us the order in which we use them.

* Basic classes: First Notepad, then EditPlus, then Eclipse.

* Employment classes: MyEclipse and Eclipse are used.

13, Java Language Foundation (HelloWorld case writing and running) (master)

* A: Define Class

* B: Write the Main method

* C: Write output statement

* D:java Program Development operation and working principle

* E: Compile and run the program

Class HelloWorld {

public static void Main (string[] args) {

System.out.println ("HelloWorld");

}

}

14, Java Language Foundation (HelloWorld case FAQ) (master)

* 1, cannot find the file (all show, let the students see what is the problem)

* A: File extension shadowing causes compilation to fail

* B: The file name is wrong

* 2, the word spelling problem (all show, let the students see what is the problem)

* A:class written as Class

* B:string written as String

* C:system Written system

* D:main written Mian

* 3, bracket matching problem (all demonstrate, let students see what is the problem)

* A: Remove the curly braces from the class body

* B: Remove the curly brace of the method body

* C: Take out the curly brace of the output statement.

* 4, Chinese and English problems (all show, let the students see what is the problem)

* A: Message: Error: illegal character: \???? The format

* Note: English characters are basically required in Java programming

XV, Java Language Foundation (Java language Writing format (conventional)) (master)

* 1, curly braces to align, and write in pairs

* 2, with a space in front of the left curly brace

* 3, encountered opening brace to indent, Tab

* 4, blank line between method and program block makes the program look clear

* 5, add spaces between statements, such as for statement

* 6, plus spaces on both sides of the operator

16, the Java Language Foundation (PATH environment variable function and configuration Way 1) (master)

* 1, the development program in the JDK Bin directory is prone to problems

* A: If there are too many files, it is inconvenient to manage

* B: Delete the unwanted files that you have written, and may accidentally remove the tool from the JDK.

* 2, how to solve the problem?

* Notepad Such commands can be executed under any path, configuring the PATH environment variable

* 3, configuration method

* A:XP System

* Right click on desktop computer → select Properties → select advanced tab → Click environment variables → find path→ in system variable double-click path→ to add the bin directory under the JDK installation directory to the leftmost and add a semicolon.

* B:WIN7/WIN8 System

* Right click on desktop computer → select Properties → select advanced system settings → select advanced tab → Click environment variables → find path→ under System variables double-click path→ to add the bin directory under the JDK installation directory to the leftmost and add a semicolon.

* path is configured with executable file. exe, which can be configured to access executable files under Path paths under different drive characters

17, Java Language Foundation (PATH environment variable configuration Method 2) (master)

* 1, first configure Java_home

* 2, then modify path

* 3, finally say that path is a sequence of relations

18, the Java Language Foundation (CLASSPATH environment variable function and its configuration) (understanding)

* 1, why to configure Classpath

* 2, the principle of classpath configuration

* 3, how to configure Classpath

* The difference between path and classpath

* path is configured with executable file. exe, which can be configured to access executable files under Path paths under different drive characters

* CLASSPATH configuration Java class file, which is the. class file

19. Java Language Foundation (EditPlus development Program and compile run) (learn)

* 1, configure shortcut key compilation run

* 2. Remove backup files

20. Java Language Basics (Overview of annotations and their classification) (master)

* 1, what is the comment

This is a single-line comment

/* This is a multiline comment */

/** This is a document comment */

* 2. Classification and explanation of annotations

* Documentation comments are not spoken at the moment, said the following explanation

* The role of annotations

* 1. EXPLANATION procedure

* 2, help us debug errors

21. Java Language Foundation (keyword overview and use) (master)

* 1, what is the keyword

* Words that are given a specific meaning by the Java language

* 2, the characteristics of the key words

* The letters that make up the keywords are all lowercase

* 3, Common keywords

* public static void class, etc.

* 4, key words to note

* Goto and Const exist as reserved words, not currently used, advanced Notepad like EditPlus, with special color tag for keywords, very intuitive

22. Java Language Basics (Overview and composition Rules of Identifiers) (master)

* 1, what is the identifier

* is a sequence of characters to use when naming classes, interfaces, methods, variables, etc.

* 2. The constituent rules of identifiers

* English uppercase and lowercase letters

* Digital

* $ and _

* Can be in Chinese but not recommended

* 3, identifier considerations

* 1, cannot use keyword

* 2, cannot start with a number

* 3, Case sensitive

For example

$abc

_x

3Hello//illegal

China

class//illegal because it is a keyword

23. Java Language Foundation (common naming rules in identifiers) (learn)

* See the meaning of the name

Class HelloWorld

Study ()//means of learning

* Hump name (camel name)

* A: Package

* Domain name Anti-write, require all the letters lowercase

* B: Class or interface

* First Letter capitalized

* If there are more than one word, the first letter of each word is capitalized (Hump logo)

HelloWorld

* C: Method or Variable

* First word initial lowercase

* If multiple words, capitalize from the first letter of the second word

Studyjava ()

* D: Constants (Custom constants)

* All Letters capitalized

* If you have multiple words, separate them with an underscore

DAY01 Summary

* CD Change Directory

Cd..

Cd\ (cd/)

CD to enter the directory name, you can have a multilevel

* Cross-platform features (understanding)

* JRE and JDK (understanding)

* Jre:java Runtime Environment

* Jdk:java Development Kit

* Configuration and function of PATH environment variable

* Java_home

*%JAVA_HOME%\BIN;

* Function: Allow all commands under the bin directory to run in any directory

* HelloWorld Case:

1. Define a class, the basic unit of a Class:java program is the class

2. Define a Main method: the entry of the program is main

public static void Main (string[] args)

3. Write an output statement in the Main method:

System.out.println ("I love Chicken Sister");

* Identifiers

Concept: Name a class, interface, variable, method

Component: English letter case, number, _, $

Precautions:

1, can not start with a number;

2, can not be the key word;

3. Strictly case-sensitive

Naming rules: Hump name, see the name of the idea

Classes and interfaces: Capitalize the first letter, if there are multiple words, the first letter of each word capitalized: helloworld,student

Variables and methods: First letter lowercase, if there are multiple words, start with the first letter of the second word capital

GetName (), Studyjava ()

Constant name (custom constant): All letters are capitalized and multiple words are underlined (_): Max_value

Package name: All lowercase, if there is a multilevel, with Dot (.) Separated, followed by the format of the domain name anti-write

Java environment variable configuration diagram Description:

Figure I,

Figure II,

JAVA-DAY01, environment variable configuration