Folders can not be found after converting a JAVA project into a runnable JAR

I hope somebody can help me with my problem. After hours of scanning all different posts concerning the abovementioned topic I now decided to answer my own question. None of the other posts solved my problem.

I want to export an existing JAVA project as runnable JAR. Therefore I'm changing all absolute references to the following:

this.getClass().getResource("/somekindofimage.png").toString();

This way I can reach all available files in the runnable JAR.

However I need to reference a folder...so I tried it the same way:

this.getClass().getResource("/somekindoffolder").toString();

which gives me the following path:

file:\C:\Users\...\1_data_collection

By creating a file and checking with "is.Directory" it returns false. I unzipped the runnable JAR. All folders, all files that are needed are included. They are attached as sources via BuildPath.

When I test the abovementioned path with Windows Explorer it directs me to the folder I'm looking for.

I'm using Eclipse Neon 2 as IDE, my JAVA Version is 1.8-0_144. Thanks in advance!