Find Java classes implementing an interface

Find Java classes implementing an interface or Class

 

Call the method "getAllClassByInterface" with a Class or interface, return all classes implemetnting it.

class ClassUtils{

	public static List<Class> getAllClassByInterface(Class c) {
		
		List<Class>  returnClassList = new ArrayList<Class>();
		try{
		if(c.isInterface()){
			String packageName = c.getPackage().getName();
			List<Class> allClass = getClasses(packageName);
			
			for(int i=0;i<allClass.size();i++){
				if(c.isAssignableFrom(allClass.get(i))){
					if(!c.equals(allClass.get(i))){
						returnClassList.add(allClass.get(i));
					}
				}
			}}}
		catch (ClassNotFoundException e) {
			e.printStackTrace();
			} catch (IOException e) {
			e.printStackTrace();
			}
		return returnClassList;
	}

	private static List<Class> getClasses(String packageName) throws ClassNotFoundException,IOException {
		
		ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
		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;
	}
	
	

	private static List<Class> findClasses(File directory,
			String packageName) throws ClassNotFoundException {
		List<Class> classes = new ArrayList<Class>();
		
		directory = new File(directory.getPath().replace("%20", " "));
		
		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().split("\\.")[0]));
			}
		}
		return classes;
	}
	
}