Thanks for the help and the link. It does run now but the application only opens for a second and then it closes again. This is the output:
Trying window - 1280x800
Window successful
Exception in thread "main" java.lang.ExceptionInInitializerError
at platformertrylwjgl.PlatformerTry.loadGame(PlatformerTry.java:55)
at platformertrylwjgl.PlatformerTry.startGame(PlatformerTry.java:46)
at platformertrylwjgl.PlatformerTry.main(PlatformerTry.java:170)
Caused by: java.lang.RuntimeException: Resource not found: res/tex/TestTexture.p
ng
at org.newdawn.slick.util.ResourceLoader.getResourceAsStream(ResourceLoa
der.java:69)
at platformertrylwjgl.graphics.TextureManager.loadTexture(TextureManager
.java:26)
at platformertrylwjgl.graphics.TextureManager.<clinit>(TextureManager.ja
va:20)
... 3 more