无法从哈希表中的对象调用方法

Question

so all I'm trying to do is create this object and then store it and others like it in a hashtable and then use ones of its methods later. But when I try and get the object and use its method I get an error.

My Code:

D_Object obj;
Hashtable player_table;

obj = new D_Object("pikachu",pikachu,PLAYER_X,PLAYER_Y,PIKA_WIDTH,PIKA_HEIGHT,PIKA_OFFSETX,PIKA_OFFSETY,PLAYER_SPEED);

player_table.put(obj.getObjNum(),obj);

....then later I try and use the objects method getObjNum() and it gives me an error

for(int i=1;i<=obj.getNumObjs();i++){
    if(player_table.get(i).getObjNum() != obj.getObjNum()){

....

the error is as follows:

appletGameExample.java:319: cannot find symbol
symbol  : method getObjNum()
location: class java.lang.Object

It gives the same error for any time I try and use the methods from this object

Can someone please help?

Answer 1

用作Hashtable<int, D_Object>

Answer 2

Because you don't specify what kind of objects the Hashtable holds, it retrieves them as Object by default (the class that everything extend s). An Object doesn't have the methods you're trying to invoke on it. You will need to perform type-casting upon accessing them, or specify what the Hashtable holds, like so:

Hashtable<String, D_Object> player_table = new Hashtable<String, D_Object>();

Answer 3

((D_Object)player_table.get(i)).getObjNum()