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This article mainly introduces "how to know the basic environment of java". In the daily operation, I believe that many people have doubts about how to know the basic environment of java. The editor has consulted all kinds of materials and sorted out simple and easy-to-use operation methods. I hope it will be helpful for you to answer the doubts about "what is the basic environment of java?" Next, please follow the editor to study!

JAVA

JAVA (the name of Java also has an interesting anecdote. One day, several members of the Java membership group were discussing a name for the new language. They were drinking Java coffee in a cafe. One of them had an idea about how his name was Java, which was appreciated by others, so the name Java spread.)

Java includes a computer programming language and a platform.

The Java programming language is a high-level language. Released by Sun Microsystems and provided as an open standard.

* the Java platform includes a Java virtual machine and a Java application program interface (API).

Java compiles the original program into bytecode (bytecode) and executes it by interpreting the bytecode in the Java virtual machine (JVM). Because of this operation mode, as long as the corresponding Java virtual machines are prepared for different computer platforms, it is very convenient to realize the cross-platform of Java language. As a result, Java is well suited for enterprise networks and Internet environments and has now become one of the most popular and influential programming languages in Internet. Java has many praiseworthy advantages, such as simplicity, object-oriented, distributed, interpretive, reliable, secure, structural neutrality, portability, high performance, multithreading, dynamic and so on.

JVM

JVM (Java Virtual Machine) (Java virtual machine)

It is a fictional computer, which is realized by simulating various computer functions on the actual computer. Java virtual machine has its own perfect hardware architecture, such as processor, stack, register and so on, as well as the corresponding instruction system. JVM shields the information related to the specific operating system platform, so that Java programs only need to generate the object code (bytecode) running on the Java virtual machine, and can run on a variety of platforms without modification. When the Java virtual machine executes the bytecode, it actually interprets the bytecode as the execution of machine instructions on the specific platform.

JRE

JRE (Java RunTime Envirment)

Java Runtime Environment (including Java Plug-in) is a product of Sun and consists of two parts: Java Runtime Environment and Java Plug-in

Java Runtime Environment (JRE) is the Java platform on which applications can be run, tested, and transferred. It includes the Java virtual machine, Java platform core classes and support files. It does not include development tools-compilers, debuggers, and other tools. JRE needs auxiliary software-- Java Plug-in-- to run applet in a browser.

The Java Plug-in software allows Java applet and JavaBeans components to run in browsers that use Sun's Java Runtime Environment (JRE), rather than the default Java runtime environment. Java Plug-in can be used with Netscape Navigator and Microsoft Internet Explorer.

JDK

JDK (Java Development Kit)

JDK is the core of the entire Java, including the Java runtime environment (Java Runtime Envirnment), a bunch of Java tools, and Java-based class libraries (rt.jar). No matter what Java application server is essentially built-in a version of JDK. Therefore, mastering JDK is the first step to learn Java well. The most mainstream JDK is JDK released by Sun. In addition to Sun, many companies and organizations have developed their own JDK, such as JDK,BEA Jrocket developed by IBM, JDK developed by GNU and so on. Among them, the JVM (Java Virtual Machine) contained in the JDK of IBM is much more efficient than the JVM contained in Sun JDK. Jrocket, which runs exclusively on x86 platform, is much more efficient on the server side than Sun JDK. But in any case, we still need to master Sun JDK first.

JDK environment variable configuration

If the directory of jdk is C:jdk

Right-click my computer. Open the properties. Then select "Environment variable" in "Advanced" and add the environment variable as follows:

JAVA_HOME: C:jdk

CLASSPATH:.;% JAVA_HOME%jrelibrt.jar;%JAVA_HOME%libtools.jar;%JAVA_HOME%lib

Pay attention to the front ";" this is absolutely indispensable. If it is not in the value of CLASSPATH, when you run the program using java on the command line, you will be prompted with a "class undefined" exception.

PATH: add;% JAVA_HOME%bin after the original field

Java platform

It is mainly divided into three technologies according to API and areas of use.

* Java SE (formerly known as J2SE)-Java Platform, Standard Edition, located on the client side, is mainly used for programming desktop applications

* Java EE (formerly known as J2EE)-Java Platform, Enterprise Edition, the enterprise version of Java2 defined on the server side, is mainly used for the development of distributed network programs, such as e-commerce websites and ERP systems.

* Java ME (formerly known as J2ME)-Java Platform, Micro Edition, mainly used in embedded system development, such as mobile phone and PDA programming

At this point, the study of "how to know the basic environment of java" is over. I hope to be able to solve your doubts. The collocation of theory and practice can better help you learn, go and try it! If you want to continue to learn more related knowledge, please continue to follow the website, the editor will continue to work hard to bring you more practical articles!

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