code: protected void writeClassMap(File file, Map<String, ? extends Collection<String>> classMap) throws IOException {
  		File baseDir = file.getParentFile();
  
  		if (baseDir.isDirectory() || baseDir.mkdirs()) {
  			//noinspection CharsetObjectCanBeUsed
  			try (PrintWriter printWriter = new PrintWriter(file, "UTF-8")) {
  				classMap.forEach((key, value) -> {
  					printWriter.print(key);
  					printWriter.print("=");
  					printWriter.println(String.join(",", value));
  				});
  			}
  		}
  		else {
  			throw new IOException(baseDir + " does not exist and could not be created");
  		}
  
  	}
docs: Helper method which writes a map of class names to the given file.
  
  @param file     The target file in which the class names should be written.
  @param classMap The class names which should be written in the target file.
  @throws IOException when the class names could not be written to the target file.