private void appendNonSeparator() {
    builder.append("[^");
    for (int i = 0; i < separators.length(); i++) {
      appendInBracket(separators.charAt(i));
    }
    builder.append(']');
  }
Appends the regex form that matches anything except the separators for the path type.
jimfs/src/main/java/com/google/common/jimfs/GlobToRegex.java