generics observer/ observable

From:
yancheng.cheok@gmail.com
Newsgroups:
comp.lang.java.programmer
Date:
27 Apr 2007 08:02:32 -0700
Message-ID:
<1177686152.534106.130670@b40g2000prd.googlegroups.com>
 Hi all

I wish to have to a generics version of observer/ observable pattern?
just like the one which is implemented in c++ template.

http://www.codeproject.com/cpp/observer_with_templates.asp

I tried the following implementation. However, I get the following
compilation error. May I know what wrongs?

C:\Documents and Settings\yccheok\Desktop\java\observer\src\jstock
\Subject.java:31: update(jstock.Subject<jstock.Observer<T>,T>,T) in
jstock.Observer<T> cannot be applied to
(jstock.Subject<TObserver,T>,T)

package jstock;

/**
 *
 * @author yccheok
 */
public class Subject<TObserver extends Observer<T>, T> {

    /** Creates a new instance of Subject */
    public Subject() {
        observers = new java.util.concurrent.CopyOnWriteArrayList<
TObserver >();
    }

    public void attach (TObserver observer)
    {
        observers.add(observer);
    }

    void _notify (T arg)
    {
        for(java.util.Iterator< TObserver > iterator =
observers.iterator(); iterator.hasNext(); ) {
            iterator.next().update(this, arg);
        }
    }

    private java.util.List< TObserver > observers;
}

package jstock;

/**
 *
 * @author yccheok
 */
public interface Observer<T> {
    public void update(Subject< Observer<T>, T > subject, T arg);
}

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