/**
the abstract interface to implement the function of distributor
*/
import java.util.ArrayList;
public  abstract class AbsSubject
{
	private ArrayList observers;
	public AbsSubject()
	{
		observers =new ArrayList();
	}
	public ArrayList getObserver()
	{
		return observers;
	}
	public abstract void registerObserver(Observer o);
	public abstract void removeObserver(Observer o);
	public abstract void notifyObservers();
	public abstract void doUpdate(double charge);
}