Использование дженериков Java с перечислениями

This is not related to generics. Switch statement for enum in java can only use values of that particular enum, thus it's prohibited to actually specify enum name. This should work:

switch(event.getId()) {
   case SELECTED:
         l.selected(event);
         break;
   case SELECTION_CLEARED:
         l.unselect(event);
         break;
}

Update: Ok, here's an actual code (which I had to change a little bit to get it to compile with no dependencies) that I've copy / pasted, compiled and ran - no errors:

AbstractEvent.java

public abstract class AbstractEvent<S, T extends Enum<T>> {
    private S src;
    private T id;

    public AbstractEvent(S src, T id) {
        this.src = src;
        this.id = id;
    }

    public S getSource() {
        return src;
    }

    public T getId() {
        return id;
    }
}

MyEvent.java

public class MyEvent extends AbstractEvent<String, MyEvent.Type> {
    public enum Type { SELECTED, SELECTION_CLEARED };

    public MyEvent(String src, Type t) {
        super(src, t);
    }
}

Test.java

public class Test {
  public static void main(String[] args) {
      fireEvent(new MyEvent("MyClass.myMethod", MyEvent.Type.SELECTED));
  }

  private static void fireEvent(MyEvent event) {
        switch(event.getId()) {
            case SELECTED:
                System.out.println("SELECTED");
                break;
            case SELECTION_CLEARED:
                System.out.println("UNSELECTED");
                break;
         }
    }
}

This compiles and runs under Java 1.5 just fine. What am I missing here?

У меня работает.

Полная тестовая программа вырезания и вставки:

enum MyEnum {
    A, B
}
class Abstract<E extends Enum<E>> {
    private final E e;
    public Abstract(E e) {
        this.e = e;
    }
    public E get() {
        return e;
    }
}
class Derived extends Abstract<MyEnum> {
    public Derived() {
        super(MyEnum.A);
    }
    public static int sw(Derived derived) {
        switch (derived.get()) {
            case A: return 1;
            default: return 342;
        }
    }
}

Вы используете какой-то особенный компилятор?

In very short, because T is erased to an Enum class, not an Enum constant, so the compiled statement looks like you are switching on the result of getID being Enum, as in this signature:

Enum getId();

When you override it with a specific type, then you are changing the return value and can switch on it.

EDIT: The resistance made me curious, so I whipped up some code:

public enum Num {
    ONE,
    TWO
}
public abstract class Abstract<T extends Enum<T>> {
    public abstract T getId();
}

public abstract class Real extends Abstract<Num> {

}

public static void main(String[] args) throws Exception {
    Method m = Real.class.getMethod("getId");
    System.out.println(m.getReturnType().getName());
}

The result is java.lang.Enum, not Num. T is erased to Enum at compile time, so you can't switch on it.

EDIT:

I tested the code samples everyone is working with, and they work for me as well, so although I suspect that this underlies the issue in the more complex real code, the sample as posted actually compiles and runs fine.

Я только что попробовал (скопировал ваш код) и не могу воспроизвести ошибку компилятора.

public abstract class AbstractEvent<S, T extends Enum<T>>
{
    private S src;
    private T id;

    public AbstractEvent(S src, T id)
    {
        this.src = src;
        this.id = id;
    }

    public S getSource()
    {
        return src;
    }

    public T getId()
    {
        return id;
    }
}

и

public class MyEvent extends AbstractEvent<String, MyEvent.Type>
{

    public enum Type
    {
        SELECTED, SELECTION_CLEARED
    };

    public MyEvent( String src, Type t )
    {
        super( src, t );
    }


}

и

public class TestMain
{
    protected void fireEvent( MyEvent event )
    {
        switch ( event.getId() )
        {
            case SELECTED:
            break;
            case SELECTION_CLEARED:
            break;
        }
    }
}