private void recurCollect(File dir, String packagePath, Set<String> ret) {
        for (File file : dir.listFiles()) {
            if (file.isFile()) {
                String fileName = file.getName();
                if(fileName.endsWith(".class")){
                    String classResource = packagePath + fileName;
                    ret.add(classResource);
                }
            }else{
                recurCollect(file, packagePath + file.getName(), ret);
            }
        }
        
    }