Re: Can this callback mechanism be generified?

Does this work? I didn't try it.  I think the "doCallback()" method is 
ok without parameterized types... same with putting an unparameterized 
type into the map.

OTOH doesn't generics just insert the casts for you?  I don't think you 
are saving any execution time here, and the code does not necessarily 
look more clear to me.


Casper Bang wrote:

> 
> 1  interface Callback
interface Callback<C>
> 2  {
> 3      String format(Object object);
   String format( C Object );
> 4  }
> 5
> 6  class Somewhere
> 7  {
> 8      Map<Class, Callback> callbacks = new HashMap<Class, Callback>();
> 9
> 10     public void installCallback(Class clazz, Callback callback)
> 11     {
> 12         callbacks.put(clazz, callback);
> 13     }
> 14
> 15     public void doCallback(Object obj)
> 16     {
> 17         Callback callback = callbacks.get( obj.getClass() );
> 18         if(callback != null)
> 19             System.out.println( callback.format( obj ) );
> 20     }
> 21 }
> 22
> 23     somewhereInstance.installCallback( Date.class, new Callback(){
      somewhereInstance.installCallback( Date.class, new Callback<Date>(
> 24         public String format(Date obj)
      public String format(Date obj)
> 25         {
> 26             Date date = (Date)obj;
              Date date = obj;
> 27             return SimpleDateFormat.getInstance().format(date);
> 28         }
> 29     });