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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