interface USB{publicvoid read();publicvoid write();}interface Wifi{publicvoid open();publicvoid close();}classPhone implements USB,Wifi{publicvoid read(){System.out.println("USB read");}publicvoid write(){System.out.println("USB write");}publicvoid open(){System.out.println("Wifi open");}publicvoid close(){System.out.println("Wifi close");}}classTest{publicstaticvoid main(String args[]){Phone phone =newPhone();//向上转型 USB usb = phone; usb.read(); usb.write();Wifi wifi = phone; wifi.open(); wifi.close();}}interface A{publicvoid funA();}interface B{publicvoid funB();}interface C extends A,B{publicvoid funC();}原文：http://www.cnblogs.com/arroneve/p/5815456.html