Re: abstract classes and generic types

Sun, 17 May 2009 16:42:13 -0700 (PDT)
On May 17, 3:29 pm, Mark Space <> wrote:

I think I came up with the same thing Giovanni did, except "put" needs
to return a String to match your example. wrote:

abstract class a<U>> {

    String calculate() { return this.put(this.my_func()); }

       abstract String put( U u );
       abstract U my_func();


Otherwise use this the same way as his example.

Note: you can' parameterize with primitives. If you want to use flo=


or int, gotta write those by hand yourself. Sorry.

Ok, I guess I'll morph this issue a bit. I came to the conclusion that
generics were the way to go, but why should I need to define a
parameter with a class to do what I want to do?

I think of the types of variables in an object as implementation
details.. But the following doesn't work:

import java.util.*;
class AA

    Set<?> example;

         example = new HashSet<Integer>();
        _setHelper(example, new Integer(1));

    private<K> void _setHelper(Set<K> parm, K key)

where I'm attempting to give the compiler a little push in the right
direction, showing that Set<K> should be linked with the ?. I would
have thought this would have worked, but no.

Of course, if I explicitly cast it - (Set<Integer>)example, it works,
but that gets rid of the point of generics, doesn't it?

So any ideas around this?

(ps - wrt language lawyering, with all respect I detest camelcase, and
will only use it if required by convention. And no - I don't go around
naming my variables mySet, etc.. I do it for example.. so thanks for
the concern, but no thanks..

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