code: public InputStream open() {
          if (path.startsWith(CLASSPATH_PREFIX)) {
              final ClassLoader loader = Thread.currentThread().getContextClassLoader();
              return loader.getResourceAsStream(path.substring(CLASSPATH_PREFIX_LENGTH));
          } else {
              final File file = new File(path);
              try {
                  return new FileInputStream(file);
              } catch (final FileNotFoundException e) {
                  return null;
              }
          }
      }
docs: Open the resource or file and return the input stream. If the path is prefixed with classpath: then it is treated
  as a classpath resource. Otherwise, it is assumed to be a file system path.
  
  @return The input stream or {@code null} if the file or resource cannot be found.