JDK (SE, EE, ME) + JRE + (PATH + JAVA_HOME + CLASS_PATH) Installation configuration explanation [original], jreclass_path

Source: Internet
Author: User

JDK (SE, EE, ME) + JRE + (PATH + JAVA_HOME + CLASS_PATH) Installation configuration explanation [original], jreclass_path

I have been a Java programmer for a while, but as a training institution, it is inevitable that many things only know how to draw images. In fact, JDK has never been studied. Java Development is available only after we have installed it.

So I just want to learn and make up for the unknown truth. O (^) o 1. What is JDK, what is included, and what is used. What is the SDK? JDK (Java Development Kit) is a Java software Development Kit (SDK ). (The SDK is not JDK below) JDK is a unique feature. The following versions are all extended based on JDK. SE (J2SE), standard edition, standard edition, is a common version. It has been renamed Java SE since JDK 5.0. EE (J2EE), enterprise edition, and enterprise edition, which are used to develop J2EE applications, have been renamed Java EE since JDK 5.0. ME (j2e-micro edition) is mainly used for java applications on mobile devices and embedded devices. It has been renamed Java ME since JDK 5.0. Without JDK, you cannot compile Java programs. To run only Java programs, make sure that the corresponding JRE has been installed. My understanding: in fact, according to the definition of the SDK, JDK is also a JAVASE-based SDK, but later other sdks are encapsulated on the SDK base of JAVASE, it cannot run without a basic SDK. Therefore, SUN calls the javase sdk jdk separately and must be installed for all developers. 2. What is JRE and jvm jre = JVM + all programs run by the auxiliary Virtual Machine JDK is the Toolkit responsible for developing Java programs, while JRE is the Toolkit developer responsible for running Java programs = both must (Development + running) user = can run the program. o (^) o 3. JVM cross-platform reason. The platform of each VM on the middle layer is the same and has a public interface for calling, however, different operating systems need to install different JRE, which can call native APIs of different systems. This allows different systems to run java programs in a unified Virtual Machine and finally feed back to the physical machine. The effect may be slightly different. Personal Understanding: in fact, Java is mainly used to replace the server. Developer: For windows development, use the development environment on windows and the Publishing Server on winodws. Real release: if the current server is still Unix, Linux, or windows, it is free of charge compared with the previous two, and the performance is better than that on windows. Therefore, a compilation can be released to different systems to facilitate development and release !!! 4. Focus on how to configure JDK 1. first, install JDK (download the Oracle website on the official website). The installation directory is -- jdk1.6.0 _ 31 (Java Development compiling environment and Toolkit) -- jre6 (the environment where the system runs Java) 2. configure environment variable 1. environment variable configuration, we first understand the differences between system variables and user variables. System variables: all login users of the entire system can access user variables: Only login users can access 2. to add environment variables, we first understand the purpose of adding environment variables: jdk1.6.0 _ 31 is not recognized by the system, and we want the software of the entire system to be able to call the operations in jdk, this must be introduced in the system, that is, to specify a folder or to the file PATH: 1: % JAVA_HOME % \ bin; 2: % JAVA_HOME % \ jre \ bin; (The window System uses PATH to find the corresponding command, so theoretically, JDK can be called by configuring the corresponding PATH.) JAVA_HOME: C: \ Program Files (x86) \ Java \ jdk1.6.0 _ 31 (specify the corresponding folder and enter % JAVA_HOME % correctly) CLASS_PATH: (the path for loading classes or packages in Java. Only the java commands in classpath can recognize them.) 1 :.; (".; "indicates the current directory) 2: % JAVA_HOME % \ bin; 3: % JAVA_HOME % \ bin \ tools. jar; 4: % JAVA_HOME % \ bin \ dt. jar; 5: After the above tutorial is configured, it will be tested ~ 1. windows -- command line -- java (running java program) 2. windows -- command line -- javac (compiling java program) 3. windows -- command line -- javadoc (view java documentation) 4. windows -- command line -- java-version (view version) ^^ (* ~ (oo) ~) ^ public number: A Programming piglet (Direct Search) blog garden blog: programming piglets www.cnblogs.com/fly-piglet/GitHub: fly-piglet github.com/fly-piglet

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