private void step(){
  casings.forEach(null);
  casings.forEach(null);
  casings.forEach(null);
  stepPipes();
  stepForwarders();
}

private void step ( ) { casings . forEach ( null ) ; casings . forEach ( null ) ; casings . forEach ( null ) ; stepPipes ( ) ; stepForwarders ( ) ; }
advance all computer parts by one step .
