Java-multi-state motherboard instance

/* Requirement: computer running instance computer running based on Motherboard */interface PCI // interface {public void open (); Public void close ();} class mainboard // motherboard {public void run () {system. out. println ("mainboard Run");} public void usepci (pCI p) {If (P! = NULL) {P. open (); p. close () ;}} class netcard implements PCI // Nic implementing the PCI interface {public void open () {system. out. println ("netcard open");} public void close () {system. out. println ("netcard close") ;}} class Soundcard implements PCI // The sound card that implements the PCI interface {public void open () {system. out. println ("Soundcard open");} public void close () {system. out. println ("Soundcard close") ;}} class duotaidemo2 {public static void main (string [] ar GS) {mainboard MB = new mainboard (); MB. run (); MB. usepci (New netcard (); MB. usepci (New Soundcard (); system. out. println ("Hello world! ");}}