What is the proper way to convert the generic type array and use it in java?

Question

Food.java

public class Food {
}

Animal.java

public class Animal<E> {
    private E[] a = (E[]) new Object[5];


    public E[] returnArray() {
        return a;
    }



    public static void main(String[] args) {
        Animal<Food> animal = new Animal<>();

        Object[] objs = animal.returnArray();
        Food[] fd = (Food[]) objs; // error happens here!
        fd[0] = new Food();


    }
}

error message

Exception in thread "main" java.lang.ClassCastException: class [Ljava.lang.Object; cannot be cast to class [Ltestsample.Food; ([Ljava.lang.Object; is in module java.base of loader 'bootstrap'; [Ltestsample.Food; is in unnamed module of loader 'app')
    at testsample.Animal.main(Animal.java:19)

error happens when I try to convert the generic type array, Food[] fd = (Food[]) objs, it seems fd and obj are both Food[] array, what's going wrong here.

The correct way to deal with mixing arrays and generics is not to use arrays: use a `List` instead. — Andy Turner, Apr 29 '20 at 12:58
But if the method return the E[] array, how to deal with it. — Alex Zheng, Apr 29 '20 at 13:06
You can cast as appropriate, but this way is "dirty", and better to avoid it as per @AndyTurner's suggestion — Hovercraft Full Of Eels, Apr 29 '20 at 13:08
You can give `Animal` a constructor accepting an `IntFunction`, which allows a correctly-typed array to be constructed. — Andy Turner, Apr 29 '20 at 13:17

What is the proper way to convert the generic type array and use it in java?

0 Answers0