Java Learning Day03 from 0-Java Classification and Development Environment Installation

Day03-Java classification and development environment installation

Java classification

1. JavaSE Standard Edition (desktop program, console development, etc.)
2. JavaME embedded development (mobile phones, small home appliances, etc.)
3. JavaEE enterprise-level development (web side, server development, etc.)

JDK、JRE、JVM

1. JDK (development environment): Java Development Kit, Java development kit, used to develop Java programs, for java developers
2. JRE (Runtime Environment): Java Runtime Environment, Java Runtime Environment, for Java users
3. JVM (the core of write once, run anywhere): Java Virtual Machine, Java virtual machine, used to interpret and execute bytecode files (Class files).

JRE is the environment for executing Java programs. JRE + development tools = JDK can develop Java programs.

JDK > JRE > JVM

JDK (Java Development Environment) installation

• Uninstall:

  1. Right-click this computer-Properties-Advanced System Settings-Environment Variables-Find System Variable Java Address-Open Address-Delete jdk file package
  2. Delete Java_Home in system variables
  3. Open the Path in the system variable-delete Java
  4. Enter java -version in Dos to view

• installation:

  Configure environment variables:

  1. Create a new system variable, name JAVA_HOME, and the address is the JDK installation address (in the JDK)

  2. Configure the path variable, create new "%JAVA_HOME%\bin" and "%JAVA_HOME%\jre\bin"

  Test whether the JDK is installed successfully:

  ​ Open dos --> enter java -version

File directory and function

1. bin: Compiler and Java running tools (java.exe, javac.exe, etc.)
2. include: reference C language header files
3. jre: java operating environment
4. lib: java class library file
5. src.zip: source code of java basic classes