Building a Java development environment

JDK VS JRE
Jdk:java Development Kit, a JAVA development environment that contains the tools needed for development
Jre:java Runtime Environment, is the Java operating environment, the role is to run Java programs
Java Knowledge points
Java executes bytecode files through the JVM.
Java is cross-platform because the JVM is not cross-platform and each operating system has its own JVM
Java is semi-explanatory half-compiled language
Java does not directly generate executable files (binaries), it compiles. java files into bytecode through the Java compiler, and then interprets bytecode as machine instructions on specific platforms through the JVM.
advantages of the Java language
the biggest advantage of the Java language is the platform-independent, can be written once, run everywhere
Java also provides automatic memory management, programmers do not need to allocate in the program, free memory
Java uses references to compensate for error-prone pointers
avoids confusion of assignment statement = and logical operation statement = =
The complex concept of multiple inheritance is removed, using the implementation of multiple interfaces
platform version of Java
Java is divided into J2SE, EE and J2ME three different platform versions, namely Standard Edition (Java 2 Platform, Standards Edition), Enterprise Edition (Java 2 Platform, Enterprise Edition) and micro- Version (Java 2 Platform, Micro Edition). Starting with Java 1.5 (or Java 5.0), they are called Java SE, Java EE, and Java ME.
the Standard Edition platform (Java SE) allows you to develop and deploy Java applications that are used in desktop, server, embedded, and live environments. In addition, Java SE contains a class library that supports the implementation of Java Web Services, so Standard Edition is the foundation of the Enterprise Edition.

The Enterprise Edition platform (Java EE) helps developers develop and deploy Java Web applications. The Enterprise Edition provides Web services, component models, management, and communications APIs that can be used to implement enterprise-class service-oriented architectures (service-oriented Architecture, SOA) and Web 2.0 applications.

The mini-version of the platform (Java ME) is mainly used for mobile devices and embedded devices, such as mobile phones, PDAs, TV set-top boxes and so on. The mini edition includes a flexible user interface, robust security model, many built-in network protocols, and support for dynamically downloadable online and offline applications. Java ME-based applications, like normal Java programs, can run on many devices with only one compilation.

Java Development and operating environment (Java SE)

1. Download the JDK

Input URL: http://www.oracle.com/index.html, browse Oracle's official homepage, select Downloads->java for Developers hyperlink

Will jump to the download page of the JDK, select the corresponding platform such as Java se->downloads, click Download hyperlink

On this page, the JDK download link for each operating system is included, and the JDK of your system is selected to download it to your local hard drive. Note that you need to read "Oracle Binary Code License Agreement for Java SE" before downloading, and you must accept the terms in order to download the JDK (select "Accept License Agreement").

2. Installing the JDK

In Windows, double-clicking the "Jdk-8u45-windows-x64.exe" file that you just downloaded will open the installation screen. Click the "Next" button, where you can select the components and installation directories you want to install.

3. Setting Environment variables

Open the Environment Variable Settings window by tapping environment variables, advanced, properties, right-click Computer. Select new, input variable named java_home and variable value (JDK installation path)

Double-click the path variable to modify it, add%java_home\bin to the front of the original variable;

You can add the path to the class lookup as needed:

CLASSPATH.; %java_home%\lib\dt.jar;%java_home%\lib\tools.jar

To test if the installation is successful, enter JAVAC in the command line window to see if the following information is displayed

4. Understanding the Java directory after installation of JDK
The tool that the Bin development needs to use, compiles the program Javac, runs the command Java and so on
Demo Development Kit comes with a demonstration program
DB uses embedded database Derby to develop the resources and some cases
Include C + + header files for compiling local methods
Jre Java Run-time environment
Library files for the LIB development Kit
Sample Development Kit comes with a case program
Src.zip class Library API source code files

Building a Java development environment