in the ProductConsumer class, but Netbeans gave me the same error message, "cannot find symbol: method messageList(), location: class ProductConsumer," so I need to create a method messageList() in ProductConsumer. Thanks.
Firstly you need to understand the product you are using: Netbeans does not produce these error messages, they come from the Java compiler; this is a Java program error. Secondly you need to look at your use of the package keyword, as I mentioned in my earlier message. And thirdly, go back to the responses that Torsten.H has given you about your use of messageList().
One of these days I'm going to think of a really clever signature.