Intellij src add folder add 2 layer folder
I find in Intellij, right click on src folder no "Add Folder/Directory" option
and find that if directly add folder in window explorer src directory,
Intellij will auto refresh and show the new added folder.
So if want to add folder to src, I can directly add folder in window explorer.
and suppose the folder name is "testtest", when new add class in the folder, in the top of class file need to declare "package testtest;", that is same pcackage name as new folder name.