Thanks Reinier. The problem with this is, it requires the calling /
working code know the Impl. And the code which operates on Parents
should also operate on Children. So I never really wanted generic
defs on the left hand side.
These are the first interface definitions I wrote.. Parent will work,
but the Child cant extend this way..
So I'm looking for something that's functionally identical to this...
interface Parent extends Iterable<Parent> { }
interface Child extends Parent, Iterable<Child> { }
All I really want to do is extend the Iterable type.. The fact that
it's it self is irrelevant I guess.
On Jan 29, 11:27 pm, Reinier Zwitserloot <[email protected]> wrote:
> Christian: Are you kidding? Of course this code won't work. It's
> missing most of the generics! You missed 12 places where you need
> generics.
>
> I can't fix your code because the snippet just doesn't give any hint
> as to what its supposed to do.
>
> You need generics parameters almost everywhere with the way you've set
> it up - you need them after:
>
> class ParentImpl<HERE>
> class ChildImpl<HERE>
>
> Parent<HERE> parent = new ParentImpl<HERE>();
> for ( Parent<HERE> p2 : parent)
>
> for (Parent <HERE> p3 : p2)
>
> Parent<HERE> p = parent.iterator().next();
>
> Child<HERE> child = new ChildImpl<HERE>();
> for (Child<HERE> c2 : child)
> for (Child<HERE> c3 : c2)
>
> Child<HERE> c = child.iterator.next();
>
> Possibly this is what you meant? The code below compiles without
> errors or warnings.
>
> import java.util.*;
>
> interface Parent<T extends Parent<T>> extends Iterable<T> {
>
> }
>
> interface Child<T extends Child<T>> extends Parent<T> {
>
> }
>
> class ParentImpl implements Parent<ParentImpl> {
> public Iterator<ParentImpl> iterator() {
> List<ParentImpl> list = new ArrayList<ParentImpl>();
> list.add(new ParentImpl());
> return list.iterator();
> }
>
> }
>
> class ChildImpl implements Child<ChildImpl> {
> public Iterator<ChildImpl> iterator() {
> List<ChildImpl> list = new ArrayList<ChildImpl>();
> list.add(new ChildImpl());
> return list.iterator();
> }
>
> }
>
> public class Tester {
> public static void main(String[] args) {
> Parent<ParentImpl> parent = new ParentImpl();
> for (Parent<ParentImpl> p2 : parent) {
> System.out.println("> " + p2);
> for (Parent<ParentImpl> p3 : p2) {
> System.out.println(">> " + p3);
> }
> }
> Parent<ParentImpl> p = parent.iterator().next();
> Child<ChildImpl> child = new ChildImpl();
> for (Child<ChildImpl> c2 : child) {
> System.out.println("> " + c2);
> for (Child<ChildImpl> c3 : c2) {
> System.out.println(">> " + c3);
> }
> }
> Child<ChildImpl> c = child.iterator().next();
> }
>
> }
>
> On Jan 29, 7:11 am, Christian Catchpole <[email protected]>
> wrote:
>
> > My brain hurts. I love Iterable, In this example, I'm trying to
> > define a Parent interface which iterates a sub-list of it's self
> > type. But I want to be able to inherit to Child and change the
> > Iterator to Child. Which in theory should work because Child is a sub
> > class of Parent. I would expect any code which can operate on Child,
> > be able to operate on Parent.
>
> > My IDE thinks the "for (Parent p2 : parent)" loops are valid, but they
> > don't compile. I think the problem is I'm not actually implementing
> > Parent with any Generic type info.. but I can't find any type
> > combinations which work. And I'd prefer to not have the implementor
> > need to pass the type info.
>
> > interface Parent<T extends Parent<T>> extends Iterable<T> {
>
> > }
>
> > interface Child<T extends Child<T>> extends Parent<T> {
>
> > }
>
> > class ParentImpl implements Parent {
> > public Iterator<Parent> iterator() {
> > List<Parent> list = new ArrayList<Parent>();
> > list.add(new ParentImpl());
> > return list.iterator();
> > }
>
> > }
>
> > class ChildImpl implements Child {
> > public Iterator<Child> iterator() {
> > List<Child> list = new ArrayList<Child>();
> > list.add(new ChildImpl());
> > return list.iterator();
> > }
>
> > }
>
> > public class Tester {
> > public static void main(String[] args) {
> > Parent parent = new ParentImpl();
> > for (Parent p2 : parent) {
> > System.out.println("> " + p2);
> > for (Parent p3 : p2) {
> > System.out.println(">> " + p3);
> > }
> > }
>
> > Parent p = parent.iterator().next();
>
> > Child child = new ChildImpl();
> > for (Child c2 : child) {
> > System.out.println("> " + c2);
> > for (Child c3 : c2) {
> > System.out.println(">> " + c3);
> > }
> > }
>
> > Child c = child.iterator().next();
> > }
>
> > }
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