Java Community | Help. Code. Learn.•4mo ago

Weird class cast behavior

So I have this code:

        class SearcherAllocator extends SearcherBase.Pointer_Alloc{
            @Override
            public Pointer call(){
           
                class JSearcher extends Searcher{

                }

                return new JSearcher();

            }
        }
        Searcher.alloc(new SearcherAllocator().retainReference());

        Searcher searcher = (Searcher) Searcher.alloc().call();

        class SearcherAllocator extends SearcherBase.Pointer_Alloc{
            @Override
            public Pointer call(){
           
                class JSearcher extends Searcher{

                }

                return new JSearcher();

            }
        }
        Searcher.alloc(new SearcherAllocator().retainReference());

        Searcher searcher = (Searcher) Searcher.alloc().call();

May look a bit messy but essentially the class hierarchy of Searcher is Searcher extends SearcherBase extends Pointer. However, even though Searcher extends Pointer, when the line

Searcher searcher = (Searcher) Searcher.alloc().call();

Searcher searcher = (Searcher) Searcher.alloc().call();

runs, it gives me this:

Exception in thread "main" java.lang.ClassCastException: class org.bytedeco.javacpp.Pointer cannot be cast to class com.niki.nativeplayer.Bridge.Searcher (org.bytedeco.javacpp.Pointer and com.niki.nativeplayer.Bridge.Searcher are in unnamed module of loader 'app')

there are two Searcher.alloc() functions, one is a setter and one is a getter. I think that part is self explanatory. I tried to replicate this error with this:

    public static void main(String[] args) {
        class Pointer{


        }
        class SearcherBase extends Pointer{


        }
        class Searcher extends  SearcherBase{

        }

        Supplier<Pointer> allocator  =()->{
            class JSearcher extends Searcher{

            }
            return new JSearcher();
        };
        Searcher searcher= (Searcher) allocator.get();
}

    public static void main(String[] args) {
        class Pointer{


        }
        class SearcherBase extends Pointer{


        }
        class Searcher extends  SearcherBase{

        }

        Supplier<Pointer> allocator  =()->{
            class JSearcher extends Searcher{

            }
            return new JSearcher();
        };
        Searcher searcher= (Searcher) allocator.get();
}

But this code ,which should be pretty much equivalent, doesn't throw that exception.

32 Replies

JavaBot•4mo ago

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Kyo-chan•4mo ago

No, nothing is self explanatory The error says you have an object that's a Pointer and you're trying to cast it to Searcher. That's not going to work The second example you show doesn't do that at all

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Weird class cast behavior