First, Java environment configuration

1. Download JDK11 first (LTS stands for long term version)

Currently there are JDK13, JDK15, etc., but it is not stable. Therefore, the LTS version is recommended

2. Choose your own installation directory (remember it)

3. Configure environment variables :(this configuration has the advantage of facilitating JDK version changes)

3.1 Configure JAVA_HOME first: Select the JDK root directory

3.2 Reconfiguring path: System environment variable

4. Check whether the configuration is successful

Second, Java program running

Three, variables,

1. Classification by data type:

1.1 Basic data type variables

1.2 Reference data type variables

Classes, interfaces, arrays

2. By declared position:

4. Operators

Identifiers

Escape characters