Java features and advantages and disadvantages, Java ME/Java SE/Java EE relationship, Java version changes, Java JDK and JRE relationship, installation of Java SE JDK

Java features:

Object orientedofCross-platformProgramming language;

Run on a virtual machine in bytecode；

Comes with a fully functional class library;

Very active open source community support.

The advantages and disadvantages of Java:

advantage: Simple, robust, and secure; cross-platform, once written, can run everywhere; highly optimized virtual machines.

Disadvantage: The syntax is cumbersome; the hardware cannot be operated directly; the GUI does not work well.

Java application range:

Applicable to: enterprise and Internet back-end development; Andriod mobile app development; big data application development.

Not applicable to: underlying operating system development; desktop application development; desktop large game development.

Relationship between Java ME, Java SE, Java EE:

Java ME： Micro Edition

Java SE：Standard Edition

Java EE：Enterprise Edition

note:

Java ME is currently used very little. We are now developing apps on the mobile side instead of using Java ME, but using Java EE.

Java version changes:

Java specification:

JSR Specification: Java Specification Requests

JCP organization: Java Community Process

The relationship between Java JDK and JRE:

The figure shows the scope of the JDK and JRE each.

Install the Java SE JDK:

We can find the Java SE JDK installation package on this page:

http://www.oracle.com/technetwork/java/javase/downloads/index.html

For the current situation, we'd better download the Java SE 8 version. Choose the 32/64-bit version based on your system.

Under normal installation, the installation directory of Java SE JDK should be automatically added to the system variable. If we open cmd, the following interface will appear after inputting javac. Otherwise, manually add the directory path to the system variable.

Enter java -version to see the installed version.

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