Re: abstract classes and generic types

Mark Space <>
Sun, 17 May 2009 17:20:21 -0700
<6R1Ql.30029$> wrote:

BTW - with the below I did find a workaround. If I say:

     private<K> void _setHelper(Set<K> parm, Integer key)
         parm.add((K) key);

ie, ie explicitly cast it, this works. But it also tells me that I'm
using unsafe operations.
This should not be unsafe - there's got to be a better solution than
this out there. Else are generics inherently unsafe?

No, they're safe, just the way you are using them isn't.

First, I want to point out that if you follow Giovanni's advice, the end
user never sees the generic declaration.

class AA<T> {}

class BB extends AA<Integer> {}

The user just uses BB as a normal class:

   BB bb = new BB();

So I don't see why you want to get rid of generics. However, if you do,
then I think something like this will work:

class AA {}

class BB {} extends AA {
   Set<Integer> example;
   BB() {
     example = newHashSet<Integer>();
     example.add( new Integer() );
     System.out.println( example );

No need for the helper method, but in this case you do need to declare
the Set<> yourself (which you were basically doing anyway when you
called "new").

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