code: public static String ensureAbsolutePath(String path, String paramName) {
          requireNonNull(path, paramName);
          if (path.isEmpty() || path.charAt(0) != '/') {
              throw new IllegalArgumentException(paramName + ": " + path + " (expected: an absolute path)");
          }
          return path;
      }
docs: Ensures that the specified {@code path} is an absolute pathMapping.
  
  @return {@code path}
  
  @throws NullPointerException if {@code path} is {@code null}
  @throws IllegalArgumentException if {@code path} is not an absolute pathMapping