javac "uses unchecked or unsafe operations" when the type is being specified

Question

The following code:

public void addGrillaListener(Stage stageToClose,Grilla listener)
{
    GrillaHandler<WindowEvent> handy = new GrillaHandler<>(listener);
    if(stageToClose!=null)
    {
        stageToClose.addEventHandler(WindowEvent.WINDOW_HIDDEN,handy);
    }
}

causes the compiler to show that message. How can I avoid it?

Extra info:

• Grilla is a Stage interface
• GrillaHandler is a EventHandler subclass that takes a Grilla as a constructor parameter
• Using JDK 7, GrillaHandler<> is allowed
• The compiler message is rather unespecific - it states that this method uses unchecked or unsafe operations
• Stage is a class provided by oracle, it's part of javafx

GrillaHandler:

public class GrillaHandler<T> implements EventHandler {

    private Grilla win;

    public GrillaHandler(Grilla win) {
        this.win=win;
    }

    @Override
    public void handle(Event t) {
        win.loadTable();
    }
}

Grilla:

public interface Grilla { 
    public void loadTable();
}

Answer 1

Change code to

public class GrillaHandler<T extends Event> implements EventHandler<T>{ 
//...
}

The JavaFX EventHandler is a paremeterized type. You are missing that one in your declaration of the GrillaHandler. You are forced to provide a type argument in your class declaration or redeclare the type parameter, as you seem to require as per your declaration.