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This article introduces what is the architecture of Java in Java foundation, the content is very detailed, interested friends can use it for reference, hope to be helpful to you.

1 preface

So far, Java is still the most widely used programming language. With the continuous growth of Java and Java community, Java is no longer a simple computer language, but also a platform, a culture, a community.

1. 1 Java technology platform

According to different technical specifications, Java is divided into three structurally independent but interdependent technical branches: Java SE (Standard Edition), Java EE (Enterprise Edition) and Java ME (simplified Edition). In addition, the development of Java not only comes from the rise of the Internet, but also Google chooses Java as the Android operating system. Groovy, Scala, JRuby, Kotlin and so on are all part of the Java platform.

Java SE

Active in the desktop domain, mainly including Java API components. This version is the core of the Java platform.

Java EE

Active in the enterprise field, including Java API components, Web components, transaction components, distributed components, EJB components, message components; combining these technologies, developers can build an enterprise application with high performance and rigorous structure, and Java EE is also the preferred platform for building SOA architecture. Java EE is an extension of Java SE.

Java ME

Active in the embedded world, it is called the reduced version because JavaME retains only some of the components in the Java API, as well as some unique components that adapt to the device. Java ME is the extension of Java SE.

1.2 Java open source culture

Java has almost become synonymous with "open source". Third-party open source software and frameworks. Such as Tomcat, Struts,MyBatis,Spring and so on. Even JDK and JVM themselves have many open source implementations, such as openJDK and Harmony.

1.3 Java strong Community

The culture of Java has created the Java community, and Java has the largest number of technical advocates and open source community support in the world, and countless forums and materials. As the saying goes, everyone gathers firewood and the flame is high!

2 composition of Java architecture

The core of Java technology is the Java virtual machine-all Java programs run on it, and Java programs can only run with the cooperation of Java virtual machine, Java API and Java,class files.

2.1 Java programming language

First of all, let's take a look at the process of a Java program from writing to final execution:

(1) An A.java program source file is programmed into an A.class binary bytecode file after executing the javac command.

(2) .class files will be loaded into memory by ClassLoader and core class libraries related to java will be loaded at the same time.

(3) call the bytecode interpreter or just-in-time compiler (java is a mixed execution of the interpreter and compiler)

(4) the execution engine calls the operating system or hardware to run

2.2 Bytecode

If the compilation result of any programming language satisfies and contains the internal instruction set, symbol table, and other auxiliary information of the Java virtual machine, the compilation result is a valid bytecode file.

The important role of bytecode: provides cross-platform support for Java. It is precisely because the source code is compiled as a bytecode file, and compared with machine instructions, bytecode can solve the problems of program security and cross-platform portability. And the source code only needs to be compiled once, and the resulting bytecode file can be run on different platforms.

2.3 Java API

The API (Application Programming Interface) application programming interface is a predefined class. The aim is to enable developers to directly use these packaged classes to do specific applications, saving programmers a lot of time and energy.

2.4 Java virtual machine

Java virtual machine (Java Virtual Machine referred to as JVM) is an abstract computer that runs all Java programs and is the running environment of Java language. Its main task is to load the bytecode inside and interpret / compile it into machine instructions on the corresponding platform.

The Java virtual machine specification defines an abstract; not an actual machine or processor. This specification describes an instruction set, a set of registers, a stack, a "garbage dump", and a method area. Once a Java virtual machine runs on a given platform, any Java program (compiled program, called bytecode) can run on that platform. The Java virtual machine (JVM) can interpret the bytecode one instruction at a time (mapping it to the actual processor instruction), or the bytecode can be further compiled by a compiler called just-in-time in the actual processor.

What are the characteristics of Java? what are the characteristics of Java? what is the 1.Java language that represents the static object-oriented programming language? it implements the object-oriented theory and allows programmers to carry out complex programming in an elegant way of thinking. 2.Java has the characteristics of simplicity, object-oriented, distributed, security, platform independence and portability, dynamic and so on. 3. Using Java, you can write desktop applications, Web applications, distributed systems, embedded system applications, and so on.

On the basis of Java Java architecture is shared here, I hope that the above content can be of some help to you, can learn more knowledge. If you think the article is good, you can share it for more people to see.

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