JAVA中什么是子包什么是基础包?

You can think about the "package" concept as the "directory" in the operating system. A common parent package will contain various of sub-packages, with each package at the same level must have a unique name but not globally.

To answer your earlier question:

1) java.lang package is a frequently used package in the JAVA language. So it is the very basic package and it is so basic that the JVM will automatically import it into your program.

2) Sub packages are those in a common package who contains them. A sub package can have one and only one parent package. right?

Hope this helps your understanding in JAVA.