Java, JDK and other introductory concepts, download and install Java and configure environment variables

First, the concept

Java is an object-oriented programming language that can be used to write cross-platform applications, which can be found in the Baidu Java Encyclopedia, which is not covered here.

Java is divided into three systems, namely:

Java SE (j2se,java2 Platform standard Edition, "Java Platform Standards Edition", contains the basic environment and core class libraries required to run Java. ）；

Java EE (J2ee,java 2 Platform, Enterprise Edition, "Java Platform Business Edition", built on the basis of the Linux SE, is used to build enterprise-class applications. ）；

Java ME (J2me,java 2 Platform micro Edition, "Java Platform mini version", mainly used in mobile phone applications. ）。

JDK:JDK (Java Development Kit)Java Development toolset. The JDK is the core of the entire Java, including the Java base Class library, the Java Runtime Environment (JRE), and the Java development tools. It is necessary for Java development to be installed.

JRE:JRE (Java Runtime Environment)Java Runtime Environment. The Java program must run with the JRE support. If the system only installs the JRE, it means that the system can run any Java program, but not Java development.

Jvm:java Virtual machine (Java vm), the JVM is a specification for computing devices, which is a fictional computer that is implemented by simulating various computer functions on a real computer. For different systems, there are different virtual machines. It is because of these different virtual machines that Java can run on different systems.

Second, download the installation

Java was originally produced by Sun, and was later acquired by Oracle, Oracle, and now downloads Java to http://www.oracle.com/.

Open Oracle homepage, click Download:

Click Javase:

Click Javase again:

into the download page, because now Java has just updated to 1.8, but many people still like the previous version, if you want to choose the previous version, to pull down, pull to the bottom, find Java Archive, click on the right download icon, enter, I choose JAVA7, click Enter, First click Accept agreement, and then according to their own computer different system download different version, but here download to register, with mailbox can, very simple, but its password requirements must have uppercase and lowercase letters and numbers, this point to note.

Third, installation (WIN7)

Install JDK Two installation prompts appear during installation of the installation directory. The first time is to install the JDK, and the second is to install the JRE. It is recommended that all two are installed in a different folder in the same Java folder. (cannot be installed in the Java folder root directory, JDK and JRE installed in the same folder will be error):

IV. Configuring environment variables

1. Configure environment variables after installing JDK: Computer → properties → advanced system settings → advanced → environment variables

2, system variable → new java_home variable. Variable value fill in the JDK installation directory:

3. System variable → find Path variable → edit, enter%java_home%\bin;%java_home%\jre\bin at the end of variable value;

(Note that there is no semicolon ";" at the end of the variable value of path, and if not, enter ";" Before entering the above code)

4.

system variable → new CLASSPATH variable, variable value filled in.; %java_home%\lib;%java_home%\lib\tools.jar (Note that there is a point in the front)

System Variable Configuration complete

Java, JDK and other introductory concepts, download and install Java and configure environment variables