code: public Set<String> getResourceNames(String folder) {
  		String path = super.getResourcePath(folder);
  		Set<String> assets = locator.listAssets(path);
  		Set<String> resourceNames = new HashSet<>();
  		for (String asset : assets) {
  			int idx = asset.indexOf(path);
  			if (idx != -1) {
  				String name = asset.substring(idx + path.length());
  				idx = name.indexOf(JawrConstant.URL_SEPARATOR);
  				if (idx != -1) {
  					name = name.substring(0, idx + 1);
  				}
  				resourceNames.add(name);
  			}
  		}
  		return resourceNames;
  	}
docs: List assets within a folder.
  
  @param folder
  the root path to the folder.
  @return a set of folder paths that match.