public static Function<String,String> fold(final int width,final String lineSeparator){
  Objects.requireNonNull(lineSeparator,"The line separator must not be null");
  if (width < 1) {
    throw new IllegalArgumentException("Width must be >= 1");
  }
  return null;
}

public static Function < String , String > fold ( final int width , final String lineSeparator ) { Objects . requireNonNull ( lineSeparator , "The line separator must not be null" ) ; if ( width < 1 ) { throw new IllegalArgumentException ( "Width must be >= 1" ) ; } return null ; }
fold a string with a given width .
