Had previously been studying java programming language, thought he had finished school on the java learn about it until recently reading a book in the "in-depth understanding of java virtual machine", they find that they've learned is just tip of the iceberg. I believe that many small partners like me, did not find out about until java technology system, will not understand Java SE, Java EE series with Java What is the relationship, today to talk about a simple java technology system.
(1) from the traditional sense, Java technology system sun's definition includes the following sections:
- Java Programming Language
- Java virtual machine on a variety of hardware platforms
- Class File Format
- Java API class libraries
- Third-party Java class libraries from the open source community and commercial organizations
Java programming language Needless to say, that is, we usually write the code, etc., we also start from the linguistics;
Java Virtual Machine is a very important part, we all know that in addition to Java object-oriented, there are many other advantages, such as: get rid of the shackles of hardware platforms, to achieve "write once", that java is how to achieve this technology it? Because the Java virtual machine has its own set of comprehensive hardware architecture and instruction set, no matter what specific operating system platform, as long as the Java program to generate object code that runs on the Java virtual machine, you can run on multiple platforms.
Class file format is the basis of cross-platform Java can, Java byte code across different virtual machines can run on different platforms, because these bytecode file format specification according to Calss make up the Class file can be based on different languages Calss generate bytecode file format that can be run on a JVM.
Java API class libraries role is also very strong, we write the code, often used import, we import fact is that Java programmers have been packaged interfaces and classes, these interfaces and classes correspond to implement certain specific functions, when we write programs directly to those interfaces and classes used to use, greatly improving the efficiency of programming. In addition, API in addition to the "application programming interface" means, but also refers specifically to the API documentation, help files, also known as, which contains a lot of java classes and methods description is written in java essential tools to help, everybody with up ah!
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third-party Java class libraries Well, I do not know what, there is little interest partner can own the Internet search a search ~
(2) If you follow the Java technology focus areas to points, Java technology system can be divided into four platforms:
- J AVA Card : Support some Java applets (Applets) running on small memory device platform (such as smart cards).
- ME Java (Micro Edition): support for running Java programs in mobile terminal platform (mobile phone, PDA), and on the Java API has been streamlined, formerly known as J2ME.
- SE Java ( Standard Edition): Support for desktop applications for the Java platform (such as application under Windows), providing a complete java core API, formerly known as J2SE.
- EE Java (Enterprise Edition): supports the use of multi-tiered enterprise applications ( such as ERP, CRM applications) Java platform, in addition to providing Java SE API, but also to add a lot of them and provides related deployment support, before It is known as J2EE.
If as I understand it, directly to their understanding as areas of concern from small to big hey hey hey ~
(3) here would also like to mention a few, the first division method, we generally put the Java programming language, Java virtual machine, Java API class libraries these three parts collectively referred to as the JDK (Java Development Kit), the JDK is Java program to support the development of the smallest environment. The general subset of the Java SE API Java API class libraries and the Java virtual machine two parts collectively referred to as the JRE (Java Runtime Environment), is to support the JRE Java program to run standard environment, both of which must be distinguished.