click on the link, the author has linked it to java's api docs type in the first couple of letters of JTextArea select JTextArea you will now be looking at the api docs for JTextArea scroll down to the Methods section - the method you want will be in this section, if you want to add onto existing text.
if you want to replace what is currently in the textArea, scroll down a bit further to the methods inherited from... the method you want is one of the set...() methods - it will stand out
the api docs are handy to have on your pc, you can download them from here
I don't understand the question. Do you mean you want to know how to write an ActionListener?
You are adding new JTextFields to your panel2; when you use the anonymous object syntax like that, you can never get access to those objects again. You will heve to give those JTextFields names, either as private fields or final local variables, before you can get your hands on them.
I have my own ideas about ActionListeners, and have written recently here. In my opinion the crucial question is:
Are you going to have several ActionListeners doing the same thing or similar things?
If yes, then write a class which implements the java.awt.event.ActionListener interface, and look in the API for its method signature. You must use exactly the same signature. Put whatever you want to do in its method body. Example:-
The alternative is to use the anonymous inner class, which you do in stages, unless you can persuade an IDE to put it together for you.
1: put in the addActionListener() method
It won't work until you finish the whole procedure.
2: break the line with two enter keystrokes in the ().