Normally you would not even have to bother with this; imagine you have an application that uses a FilenameFilter to retrieve some resource from within your project. Say you want to load all image files in a specific location that conform to „/images/imagePrefix*_imageSuffix.png“. To create a FilenameFilter to retrieve a list of all file names that conform to that pattern is not that difficult. So you have an application that runs happily ever after … until you create a jar file from your project.