JDK (SE, EE, ME) + JRE + (PATH + java_home + class_path) installation configuration in detail "original"

I am a Java introduction has a period of time programmer, but as a training institutions out, inevitably a lot of things only know the picture gourd, in fact, the real JDK is what has not been studied. Just know that we have installed to do Java development.

So I came to learn, and to make up the unknown truth. O (^▽^) o , what the JDK is, what it contains, and what it does. What is the SDK?     JDK (Java Development Kit) is the Java Language Software Development Kit (SDK).     (the SDK is not the JDK) the JDK is unique and the version is expanded on a JDK basis.     SE (J2SE), Standard Edition, is a version we typically use, starting with JDK 5.0 and renaming Java SE.     EE, Enterprise Edition, Business Edition, uses this JDK to develop the Java EE application, starting with JDK 5.0, and renaming it to the same.     ME (J2ME), Micro Edition, primarily for Java applications on mobile devices, embedded devices, starting with JDK 5.0, renamed Java ME.     Cannot compile Java programs without JDK, if you want to run only Java programs, make sure the appropriate JRE is installed.   Personal Understanding:    In fact, according to the SDK definition, JDK is a kind of javase-based SDK, but then the other SDK is in the Javase SDK based on the package, no basic SDK can not run.     So Sun has called the Javase SDK a single JDK and must be installed for all developers.   II, what is the JRE and jvm    JRE = JVM + All programs run by the secondary virtual machine     JDK is the toolkit responsible for developing Java programs     While the JRE is the toolkit for running Java programs      developer = Both (development + run)     user = able to run the program can be O (^▽^) o  Three, the JVM cross-platform reasons, the middle layer & nbsp   Each virtual machine's platform is the same, with a common interface to make calls, but different operating systems need to install different JRE, can invoke the native API of different systems.     Enable different systems to run Java programs with a unified virtual machine, and finally feed back to the physical machine。 The effect may be slightly different.   Personal understanding: In fact, Java cross-platform is mainly in the server-side replacement above.     Developers: Using Windows Development, using the development environment above windows and the publisher in Winodws.     Real release: On the current server or UNIX, Linux, Windows, compared to the previous two is free, and performance is better than the performance above windows.      So a real compilation can be published to different systems, convenient development and easy to publish!!!   Four: Focus on how we configure jdk    1. Install the JDK first (official website download Oracle website)         installation directory        --JDK1.6.0_31 (Environment and Toolkit for Java Development Compilation) & nbsp      --JRE6 (System running Java environment)     2. Configure environment variables         1. environment variable configuration, we first understand the difference between system variables and user variables             System variables: All users of the entire system can access the         & nbsp   User variables: Users who can only specify logins can access         2. Add environment variables             First we understand the purpose of adding environment variables:            is itself jdk1.6.0_31 to and is not recognized by the system, want the entire system software can invoke the operation inside the JDK, must be introduced in the system             This side of the situation is to specify the folder or specified within the file             path:              &nbsp 1:%java_home%\bin;                2:%java_home%\jre\bin;      &NBS P       (the window system is looking for the corresponding command through path, so the theory is that the corresponding PATH,JDK can be called as long as it is configured)             Java_ Home:c:\program Files (x86) \java\jdk1.6.0_31 (assigned to the corresponding folder, can be correctly populated into%java_home%)             Class_path: (The path to the Java load class or package, only in classpath that the Java command can recognize) 1:.; (".;"                Represents the current directory) 2:%java_home%\bin;                3:%java_home%\bin\tools.jar; 4:%java_home%\bin\dt.jar, five: After configuring the above tutorial, it is testing, O (∩_∩) o haha ~ 1. windows--"command line-Java (running Java program) 2. windows--"command line--" Javac (compiled Java program) 3. windows--"command line--" Javadoc (view Java document) 4. windows--command line--"java-version (view version)---------------------------------------------------------------------^ (*￣ (oo ￣) ^ Public number: Trying to program the piglet (direct search) Blog Park Blog: try to program the piglet Www.cnblogs.com/fly-piglet/GitHub:fly-piglet Github.com/fly-piglet

JDK (SE, EE, ME) + JRE + (PATH + java_home + class_path) installation configuration detailed "original"