👀 Views: 4 💬 Answers: 1 📅 Created: 2025-06-08

java reflection generics classcastexception Java

I can't seem to get I've been banging my head against this for hours. I'm working with a `ClassCastException` when trying to access fields of a generic type using reflection in Java 17. My setup involves a generic class `Container<T>` that holds a list of items of type `T`. I want to dynamically retrieve and cast the field of type `List<T>` from an instance of `Container<String>`, but I'm running into issues. Here’s a simplified version of my code: ```java import java.lang.reflect.Field; import java.util.ArrayList; import java.util.List; public class Container<T> { private List<T> items = new ArrayList<>(); public void addItem(T item) { items.add(item); } } public class Main { public static void main(String[] args) { Container<String> stringContainer = new Container<>(); stringContainer.addItem("Hello"); try { Field field = stringContainer.getClass().getDeclaredField("items"); field.setAccessible(true); List<String> retrievedItems = (List<String>) field.get(stringContainer); System.out.println(retrievedItems); } catch (NoSuchFieldException | IllegalAccessException e) { e.printStackTrace(); } } } ``` When I run this code, I receive the following behavior: ``` Exception in thread "main" java.lang.ClassCastException: java.util.ArrayList want to be cast to java.util.List ``` I suspect it has something to do with type erasure in Java generics, but I thought that casting to `List<String>` should work since I know the type at runtime. Is there a way to properly handle this scenario to avoid the `ClassCastException`? I've tried various casting approaches and also checked the runtime object type with `getClass()`, but I still receive the same behavior. My development environment is Windows. What am I doing wrong? I'm coming from a different tech stack and learning Java. Cheers for any assistance! For context: I'm using Java on macOS.