import java.util.ArrayList;
import java.util.List;

public class Sample6 {
    
    public static void main(String[] args) {
        List<MobileDevice> list = new ArrayList<>();
        list.add(new MobilePhone("PPP"));
        list.add(new Tablet("QQQ"));
        list.add(new Tablet("RRR"));
        list.add(new MobilePhone("SSS"));
        
        for (MobileDevice device : list) {
            device.feature();
        }
    }
}