How do I gain type safety with a generic method taking a class object?

Question

How do I achieve type safety with the following code without getting a compile error?
import java.util.ArrayList;
import java.util.List;
public class Main {
    public static void main(String[] args) throws Exception {
        ListenerHolder th = new ListenerHolder();
        List<TestObject<String>> list = createTestObjectList();
        /* *** compiler error here *** */
        th.addListener(TestObject.class, list);
    private final static List<TestObject<String>> createTestObjectList() {
        List<TestObject<String>> list = new ArrayList<TestObject<String>>();
        return list;
    private final static class ListenerHolder {
            /* *** my generic method *** */
            public <T> void addListener(Class<T> listenerType, List<T> listener) { }
    private final static class TestObject<T> { }
}The compiler error is:
C:\java\Main.java:11: <T>addListener(java.lang.Class<T>,java.util.List<T>) in Main.ListenerHolder cannot be applied to (java.lang.Class<Main.TestObject>,java.util.List<Main.TestObject<java.lang.String>>)
Thanks in advance,
Dan

Answer 1

dandubois wrote:
Thanks for the help, that is exactly what I wanted to know.
It didn't occur to me that TestObject<T> would in some respects be considered as an 'extends' of TestObject as I know the compiler converts them all back to plain TestObjects.Maybe I should have written TestObject<?>, to make it more obvious. There's some supertype/subtype relation diagram in the Generics FAQ somewhere, if you need more detailed information.
In the end, I think jtahlborn's solution might be more appropriate in the described scenario, so you should go for it.