Calling a method from an abstract class in a seperate class

I am trying to call the getID() method from the Chat class in the getIDs() method in the Outputter class. I would usually instantiate with a normal class but I know you cant instantiate the method when using abstract classes. I've been going over and over my theory and have just become more confused??
Package Chatroom
public abstract class Chat
   private String id;
   public String getID()
      return id;
   protected void setId(String s)
      id = s;
   public abstract void sendMessageToUser(String msg);
Package Chatroom
public class Outputter
public String[] getIDs()
     // This is where I get confused. I know you can't instantiate the object like:
        Chat users=new Chat();
        users.getID();
I have the two classes in the package and you need to that to be able to use a class' methods in another class.
Please help me :(

I have just looked over my program and realised my class names are not the most discriptive, so I have renamed them to give you a clearer picture.
package Chatroom
public abstract class Chatter
private String id;
public String getID()
return id;
protected void setId(String s)
id = s;
I am trying to slowly build a chatroom on my own. The Chatter class is a class that will be used to represent a single logged in user and the user is given an ID when he logs in through the setId and getID() methods.
package Chatroom;
import java.util.Vector;
public class Broadcaster
private Vector<Chatter> chatters = new Vector<Chatter>();
public String[] getIDs()
// code here
The Broadcaster class will keep a list of all logged-in users keeps a list of all the chats representing logged-in users, which it stores in a Vector.I am trying to use the getIDs() method to return an array of Strings comprising the IDs of all logged-in users, which is why im trying to use the getID() method from the Chat class.
I apologise if I come across as clueless, it's just I have been going through books for about 4 hours now and I have just totally lossed all my bearings

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