How to mark package as a resource folder?

This can be solved in several ways. An example of a good approach would be the following folder structure:

src
  main
     java
     resources
  test
     java
     resources

When this is done, you put all you java classes under src/main/java/com.mycompany package and any resources under /src/main/resources/com/mycompany folder.

To link them together, go to the project properties, and find the Path tab. Mark the src/main/java and src/main/resources as source folders. (see the screen-shot attached)

If you link them together, you'll be able to use getResourceAsStream() method. If you wonder why you should use the following folder structure - this is standard maven way of keeping things clean and tidy.

Directories Creation

Intellij creates directories when you ask her to create package. It is not an error.

If you create package "com", it will create the dir "com", and if you create a source file there, it will think that the file is in the package "com".

If you create package "com.next.pack", it will create three nested dirs "com", then "next", then "pack", and if you create a source file there, it will think that the file is in the package "com.next.pack".

Directories Structures

Only the path under the source root is taken as a package. Any directory(ies) can be set as a source root(s).

Resources roots

Make practically any structure of directories. Somewhere in it there is the root dir of resources. Right-click it and Mark Directory As ... Resources Root.

Notice, the same method can be used for the directories structures for tests, test classes, and test resources. Look here.