That's because the listener does not have a reference to the TextField.
You need some reference to something that can then get access to the TextField.
So you can do this many ways.
In your Listener class you only have the ActionEvent which will only return the Button. But
you should be able to get a hold of its container the JPanel Holder. Change the name to lowercase to meet the Coding Standard set by
Java.
So the question then becomes, can you get to the TextField from there. Does JPanel have a method to get all the Components that are in the Panel. And then loop through those till you find the TextField.
Personally, that is the long way around. and with OO techniques, it would be easier, but that would take a long time to describe. But basically you would have more classes, like the JPanel Holder being a class with a method called setMessage() and that class has an instance variable holding the JTextfield, that that method setMessage() can simple call the TextFields setText() method.
Mark