public static CharMatcher javaIsoControl() {
    return JavaIsoControl.INSTANCE;
  }

  /**
   * Determines whether a character is invisible; that is, if its Unicode category is any of
   * SPACE_SEPARATOR, LINE_SEPARATOR, PARAGRAPH_SEPARATOR, CONTROL, FORMAT, SURROGATE, and
   * PRIVATE_USE according to ICU4J.
   *
   * <p>See also the Unicode Default_Ignorable_Code_Point property (available via ICU).
   *