docs: public InputStream getResourceAsStream(String fileName)
      {
          try
          {
              File file = getFile(fileName);
              cache.put(fileName, new CacheEntry(file));
              return new FileInputStream(file);
          }
          catch (FileNotFoundException e)
          {
              InputStream is = 
                  Thread.currentThread().getContextClassLoader().getResourceAsStream(fileName);
              if (is != null)
              {
                  cache.put(fileName, new CacheEntry());
              }
              return is;
          }
      }