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interface Usb{       void work();}
   
class Phone_ implements  Usb{       @Override    public void work() {           System.out.println("??????...");    }    public void call() {           System.out.println("???????");    }}
   
class Camera_ implements Usb{       @Override    public void work() {           System.out.println("??????...");    }}
   
public class InterfacePolyArr {       public static void main(String[] args) {           // ????        Usb[] usbs = new Usb[2];        // ????????????????????        usbs[0] = new Phone_();        usbs[1] = new Camera_();        for (int i = 0; i < usbs.length; i++) {               usbs[i].work();            // ??????            if (usbs[i] instanceof Phone_) {                   // ????                ((Phone_) usbs[i]).call();            }        }    }}
   
   

???????????????????????????Usb???????Phone_?Camera_???????????????????????????????????