Internal File-Access in Applet doesn´t work

Hello,
i want to read Data from a file (e.g. Config). I tried it on two ways, one where I placed it in the assets folder and one to place it in the same package.
Both gave me the following Exception:

INFO: [0121] Screen.startScreen(10)
Exception in thread “LWJGL Renderer Thread” java.security.AccessControlException: access denied (java.io.FilePermission assets\Sensor1.txt read)
at java.security.AccessControlContext.checkPermission(Unknown Source)
at java.security.AccessController.checkPermission(Unknown Source)
at java.lang.SecurityManager.checkPermission(Unknown Source)
at java.lang.SecurityManager.checkRead(Unknown Source)
at java.io.FileInputStream.(Unknown Source)
at java.io.FileInputStream.(Unknown Source)
at java.io.FileReader.(Unknown Source)
at wsn.Controller.(Controller.java:59)
at wsn.InteractionController.(InteractionController.java:27)
at wsn.Main.simpleInitApp(Main.java:131)
at com.jme3.app.SimpleApplication.initialize(SimpleApplication.java:225)
at com.jme3.system.lwjgl.LwjglAbstractDisplay.initInThread(LwjglAbstractDisplay.java:130)
at com.jme3.system.lwjgl.LwjglAbstractDisplay.run(LwjglAbstractDisplay.java:207)
at java.lang.Thread.run(Unknown Source)

What am I doing wrong? Or how do i have to handle it to get a file read in my applet?

Thanks for your help!

Best Regards,
Pascal

Load it via the classloader as shown in the examples, not via a java.io.File