javaobjectinterfacecasting

cast from List<MyClass> to List<Interface>

I think I made some mistake while writing my code. I have a class MyClass that implements Interface, now I've a method that is generic for List of Interface as a parameter. I want to use my method by passing a List. I can't cast from List to List (that I assumed I could). So, what can I do to make my code work? here an example:

List<MyClass> lista = returnMyClassList();
myMethod((List<Interface>) lista); //this doesn't work

//myMethod signature
public void myMethod(List<Interface> struttura);

Thanks for helping.

Solution

  • Use an upper bound of Interface for the type: <? extends Interface>.

    Here's some compilable code that uses classes from the JDK to illustrate:

    public static void myMethod(List<? extends Comparable> struttura) {}

public static void main(String[] args) {
    List<Integer> lista = null;
    myMethod(lista); // compiles OK
}