java - return class names not working in Jar -

i have used code list of class names package:

private list<string> getclasses() {     list<string> classes = new arraylist<string>();     string packagename = "algorithm/impl";      url directoryurl = thread.currentthread().getcontextclassloader().                         getresource(packagename);      file directory = new file(directoryurl.getfile());      if(directory.exists())     {     string [] files = directory.list();     for(string filename : files)     {         classes.add(filename.substring(0, filename.lastindexof(".")));     }     }     return classes; } 

but not work when app packaged executable jar file. why?

you can make use of class jarfile.

jarfile file = new jarfile("yourfilename.jar");    (enumeration<jarentry> enum = file.entries(); enum.hasmoreelements();) {        jarentry entry = enum.next();        system.out.println(entry.getname());    } 

or if want search particular class inside jar can use zipfile class.

                jarfile jar = new jarfile(yourjarfile);                 zipentry e = jar.getentry(class_file_to_find);                 if (e == null) {                     e = jar.getjarentry(class_file_to_find);                     if (e != null) {                         foundin.add(f.getpath());                     }                 } else {                     foundin.add(f.getpath());                 }