Get All Classes Within A Package

http://dzone.com/snippets/get-all-classes-within-package


public static void main(String[] args) throws Exception{
String packageName = "a.b.c.d";

List<?> list = getClasses(packageName);
System.out.println(list);
}

/**
* Scans all classes accessible from the context class loader which belong to the given package and subpackages.
*
* @param packageName The base package
* @return The classes
* @throws ClassNotFoundException
* @throws IOException
*/
public static List<?> getClasses(String packageName) throws ClassNotFoundException, IOException {
   ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
   assert classLoader != null;
   String path = packageName.replace('.', '/');
   Enumeration<URL> resources = classLoader.getResources(path);
   List<File> dirs = new ArrayList<File>();
   while (resources.hasMoreElements()) {
       URL resource = resources.nextElement();
       dirs.add(new File(resource.getFile()));
   }
   ArrayList<Class<?>> classes = new ArrayList<Class<?>>();
   for (File directory : dirs) {
       classes.addAll(findClasses(directory, packageName));
   }
   return classes;
}

/**
* Recursive method used to find all classes in a given directory and subdirs.
*
* @param directory   The base directory
* @param packageName The package name for classes found inside the base directory
* @return The classes
* @throws ClassNotFoundException
*/
private static List<Class<?>> findClasses(File directory, String packageName) throws ClassNotFoundException {
   List<Class<?>> classes = new ArrayList<Class<?>>();
   if (!directory.exists()) {
       return classes;
   }
   File[] files = directory.listFiles();
   for (File file : files) {
       if (file.isDirectory()) {
           assert !file.getName().contains(".");
           classes.addAll(findClasses(file, packageName + "." + file.getName()));
       } else if (file.getName().endsWith(".class")) {
           classes.add(Class.forName(packageName + '.' + file.getName().substring(0, file.getName().length() - 6)));
       }
   }
   return classes;
}