Re: ArrayList called with specific object constructors

From:
Lew <noone@lewscanon.com>
Newsgroups:
comp.lang.java.programmer
Date:
Tue, 28 Apr 2009 20:59:40 -0400
Message-ID:
<gt88pt$779$1@news.albasani.net>
Alessandro wrote:

The idea is that you want to be able to use a factor of Integers (e.g.)
to fill a list of Numbers. The other way of doing this is to do this:
public <T> List<? super T> makeList(Factory<T> factory)


That's clear, but I have problems with calling the interface Factory.
Still viewed Robert code but it can't work because instantiating an
interface.


You don't instantiate interfaces. You instantiate a concrete class and assign
its reference to an interface-typed variable.

This is my edited fragment:

//START
*** Factory interface ***
public interface Factory<T> {
 public T makeObject(String s1, String s2);
}

*** class calling generic method (implements Factory ??? implements
Factory<T> ???***
...
ArrayList<Ric> ricList=xmlService.xml2ListGEN(new Factory<Ric>());


Nope. Instead of 'new Factory <Ric>()' try something like Robert Klemme's
anonymous class trick, or define a named class like:

public class RicFactory implements Factory <Ric>
{
   public Ric makeObject( String s1, String s2 )
   {
     return new Ric( s1, s2 );
   }
}
====
  List <Ric> rics = makeList( new RicFactory() );
  ...

--
Lew

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