Three phases of Java:
Javase: Basic syntax, object-oriented (OOP), common classes, collections, IO streams, network programming, multi-threading, reflection,
Javaweb, front-end Basics (HTML (h5), Css,js), front-end framework (jquery,bootstrap ...), HTTP protocol, Tomcat service, Servlet (can output Dynamic Web pages), JSP ( Can write Java code HTML page), MySQL (key)/ORACLE,JDBC (Java Connection database), filters and listeners, XML parsing ...
Java EE: Application platform for enterprise-level development ..., struts2,spring (Focus), hibernate (old frame), Spring,spingmvc,mybatis (SSM framework), SSM three framework integration
Java Basic Syntax:
Learn what Java is
Java: Simplicity, robustness, distributed management,
Open Source (opensource)
Cross-platform (Kua OS)
Java language: Born in 1990.
"OAk"-----> "Javanese"---->java
Which company is Java? 1990 Sun--->2010, was acquired by Oracle.
Jdk:java Develop Kit:java Development Kit
JDK version: 1.0----> 1.5 (watershed)--->1.6--->1.7 (commonly used on the market)---->1.8 (5 large interface, lambda expression---)
Jre:java Runtime Environement:java Operating environment
JRE: All Java Core class libraries and JVMs (Java virtual machines)
JDK: Contains the JRE and all core class libraries
Jdk:www.oracle.com
Fool installation----> Next step---> Do not chinese path---> do not have special characters
After the JDK installation is complete, tip: If you need to install JRE, in case, install JRE, next;
Java Platform version
J2SE: Standard Edition: Open for desktop applications
J2ME: and embedded related solutions .... (Mobile: Android: Android Basics: Activity, broadcast push service) iOS---C language
Java EE: A set of solutions for enterprise-level development ...
Learn the core technology of EE
13 Medium Technology
Servlet,xml parsing, JSP, filters, listeners, internationalization, etc...
Enter the DOS console mode:
1) Press and hold shift--> desktop right----> Open command line Prompt here
2) Start Menu---> All programs----> Accessories----> Command line prompt
3) Windows key +r key----> Input cmd, enter DOS console
HelloWorld case
Development tools:
Notepad:windows himself with a notepad
EditPlus
notepad++: Advanced Notepad
Eclipse:java development tool (will automatically compile Java files)
The most basic unit class in Java
HelloWorld the development steps of the case:
1) No PATH environment variable is currently configured, create a new text file and name the text file: HelloWorld
2) Start editing content:
Fixed format
Class helloworld{
public static void Main (string[] args)} {
System.out.println ("Hello World");
}
}
After you finish writing, Ctrl+s Save the Code
3) Change the extension of. txt to--->.java
4) You need to compile and run Java files on the DOS console
5) must be in the bin directory of the current JDK installation directory: Set the path to this path
Using the Javac command, compile the command
Javac Java source file (Xxx.java)-----> Enter---> no error----> Generated: Class name. class (bytecode file)
Java command: Run the command (prefix that runs the bytecode file)
Java HelloWorld----> output the contents of the "HelloWorld" string
What is the reason for configuring the PATH environment variable?
Because all of the current Java files are written in the bin directory of the JDK installation directory, the late large number of Java files may not be written in the bin directory, not conducive to management, need to be in any directory on the current computer can run the Java file
Mode 1:
1) Copy the path to the bin directory of the JDK installation directory to my Computer for example
D:\JavaJDK1.8\bin
2) Computer---> Right----> Properties----> Advanced system Settings---> Environment variables---> System variables
--->path environment variable----> Press the Home key,-----> Copy D:\JavaJDK1.8\bin in Path, end of semicolon (English punctuation)
Way 1 Disadvantage: Once the JDK directory changes or JDK upgrade, need to change in path, may mistakenly delete other software/system environment variables, may cause some problems!
Mode 2: Computer---> Right----> Properties----> Advanced system Settings---> Environment variables---> System variables
Create a new variable in the system variable
Variable name: java_home
Variable Value: D:\JavaJDK1.8
PATH environment variable:--->%JAVA_HOME%\bin;
Benefit: Do not need to modify the PATH environment variable directly, but modify the variable Java_home
Java Basic Syntax:
A: Keywords
Words that are given a particular meaning by the Java language,
These keywords have a special color tag in notepad++ or in development tool eclipse
Class,public (permission modifier), void (return value), static (static modifier) ......
Attention:
Goto and const are used as reserved words, not currently used!
B: identifier: A sequence of characters giving names to classes/interfaces, variables/methods, etc.
Javar Introductory first lesson content carding
