Hello World!

This is my code:

public class Queue implements Iterable
{
       //...
    private class QueueNode implements Comparable<QueueNode>
    {
        Comparable data;
               //...
        public int compareTo(QueueNode node)
        {
            return data.compareTo(node.getData());
        }
    }
}

This is the warning:

Queue.java:25: warning: [unchecked] unchecked call to compareTo(T) as a
member of the raw type java.lang.Comparable
                       return data.compareTo(node.getData());
                                            ^
1 warning

I hope to receive answers to two questions.

1. First, will someone that is familiar with generics please modify the
syntax involved with the generics of this code so that it will compile
successfully and without any warnings?

2. Second, As I was trying to figure this out on my own I read
somewhere that because of generics the Comparable interface is not the
same thing as the Comparable<T> interface. I am hoping that someone
will either explain the difference to me or point me to documentation
somewhere that will explain the difference between these two
interfaces. And if you understand the difference between the two
interfaces, do you recommend that I use Comparable data or
Comparable<?> data inside the QueueNode object? And if your
recommendation is that I use Comparable<?>, will you please give me
some information about the ? in the generics syntax.

3. Thank you for taking time to read this and I appreciate your help if
you decide to give it.

Elliot