Generics and ArrayList.toArray(T[] a)

From:
Ian Wilson <scobloke2@infotop.co.uk>
Newsgroups:
comp.lang.java.programmer
Date:
Thu, 11 Jan 2007 17:42:13 +0000
Message-ID:
<qPednUR_Xe1n6zvYRVnyuAA@bt.com>
I don't see how to elegantly satisfy toArray(T[] a) in an abstract class.

The code below works but I'd rather avoid the need for the setType()
which instantiates an T[] for .toArray(). Obviously I cant instantiate
an T[] in the abstract class.

Is there a better way?

----------------------------------------------------
import java.util.ArrayList;

public class ArrayListProblem {
     public static void main(String[] args) {
         FooModel model = new FooModel();
         String[] fooCodes = model.getCodes();
         for(int i = 0; i<fooCodes.length; i++) {
             System.out.println(fooCodes[i]);
         }
     }
}

abstract class AbstractCodeModel<T> {
     private ArrayList<T> codes = new ArrayList<T>();
     private T[] type;

     void addCode(T item) {
         codes.add(item);
     }

     void setType(T[] t) {
         this.type = t;
     }

     public T[] getCodes() {
         return codes.toArray(type);
     }
}

class FooModel extends AbstractCodeModel<String> {
     FooModel() {
         setType(new String[0]);
         addCode("A");
         addCode("B");
     }
}
--------------------------------------------------------
The above is greatly simplified, in reality the abstract class contains
lots of code that would otherwise be duplicated in what are now its
subclasses.

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