> The simple approach is to simply add a children() method to the interface and implement it in every kind of node. Very tedious, and boilerplaty as hell.
The best approach without boilerplate would be to generate this at compile time, not runtime. You could use an approach like in http://hannesdorfmann.com/annotation-processing/annotationpr... to create at compile-time, using reflection, a ChildWalker class that accesses the relevant properties for every class annotated with @Node. At runtime, the JIT should get this down to a vtable lookup and field lookups - just about as optimized as you can get.
EDIT: Always remember https://xkcd.com/1205/ - if it would take 5 seconds to write each children() method, and you write no more than 5 Node classes per day (amortized), then you shouldn't spend more 12 hours writing the code for this blog post ;) Unless, of course, that was the point all along!
The best approach without boilerplate would be to generate this at compile time, not runtime. You could use an approach like in http://hannesdorfmann.com/annotation-processing/annotationpr... to create at compile-time, using reflection, a ChildWalker class that accesses the relevant properties for every class annotated with @Node. At runtime, the JIT should get this down to a vtable lookup and field lookups - just about as optimized as you can get.
EDIT: Always remember https://xkcd.com/1205/ - if it would take 5 seconds to write each children() method, and you write no more than 5 Node classes per day (amortized), then you shouldn't spend more 12 hours writing the code for this blog post ;) Unless, of course, that was the point all along!