🚀 go-pugleaf

Michael Rachow <michael@famrachow.de> wrote:
> Hi Dick
[snip]
> Only if you let all your different classes implement an Interface that
> requirers that method
> to be defined you can throw away all these instanceof staments and cast all
> these
> different instances to that interface and call that method.
> You can even store now all these instances under that interface and have not
> to cast anymore.
> Ok


Yes.  One common example of this is the Runnable interface.  Classes
which implement this interface provide a run() method.  This allows 
any Runnable to be passed into Thread's constructor and turned into
a thread, no matter what parent class those objects extend.

It even allows you to define an anonymous class as a Runnable, something
like this:

  public void actionPerformed( ActionEvent ae ) {

    Runnable runnableFoo = new Runnable(
      public void run() {
        ...
        // do much work here
        ...
      }
    );
    
    ...

    Thread serverReader = new Thread( runnableFoo, "Runnable Foo" );
    serverReader.start();
  }


I have something similar to this in one of the classes I wrote this
morning.  The runnableFoo is a long-lived process that opens a socket
to a remote machine and chats with it a while.  The actionPerformed()
method is called from a JMenuItem.  By starting placing all the 
long-lived work inside a Runnable, I can pass just that work into a
thread of its own.  This gets the work off the Swing/Awt Event thread
so that my GUI doesn't freeze and stop painting until the long-lived
thing finishes.  Which is exactly what it did when I had the body
of runnableFoo within the actionPerformed() method.

-- 
Joi Ellis (TeamB)               http://www.teamb.com/
No direct email, please.
For best results, post on news server newsgroups.borland.com!
Newsgroup Info: http://www.borland.com/newsgroups/guide.html