1 import java.util.*; 2  3 public class SixDuo { 4     public void eat(){ 5         System.out.println("狗狗吃骨头"); 6     } 7     public static void main(String[] args){ 8         ArrayList<Object> myAL = new ArrayList<Object>(); 9         SixDuo Dogc = new SixDuo();10         Object obj = new Object();11         myAL.add(Dogc); //加入myAL12         myAL.add(obj);13         Object o = myAL.get(0); //取出在myAL里排第一位的Dogc14         SixDuo d1 = (SixDuo)o; //将类型转换成SixDuo15         d1.eat();16         if(o instanceof SixDuo){ //为了防止o取出的不一定是SixDuo类型而进行判断17             SixDuo d2 = (SixDuo) o;18             d2.eat();19         }20     }21     22 }