工厂模式将一个接口下所有子类的实例化过程封装起来，从而增加了系统的扩展性，并且可以减少代码日后的维护量。
interfaceiplug{voidstart();
}classTVimplementsIPlug{publicvoidstart(){
System.out.PRintln("TV start");
}
}classAirConimplementsIPlug{publicvoidstart(){
System.out.println("AirCon start");
}
}classFactory{publicstaticIPlug getInstance(String className){if("TV".equals(className)){returnnewTV();
}elseif("AirCon".equals(className)){returnnewAirCon();
}else{returnnull;
}
}
}publicclassfactoryDemo {publicstaticvoidmain(String[] args) {//TODO Auto-generated method stubIPlug ip = Factory.getInstance("TV");
ip.start();
ip= Factory.getInstance("AirCon");
ip.start();
}
}