managing classes and threads java

managing classes and threads java

Here's the situation:

As you saw in that picture, I have a JFrame (main.java) and a class
(update.java). The JFrame has all the swing elements (labels, buttons,
etc), and "update.java" class has methods to perform a software update, as
shown there.
However, I realized the mistake was in the swing elements. "Update.java"
class couldn't "find" the swing elements of "main.java" form. So what I
did was to put, instead of:
JTextArea estado;
JTextField updatedVersion;
JLabel updatedLabel;
I put this :
private JTextArea estado;
private JTextField updatedVersion;
private JLabel updatedLabel;
And then when I run the program it throws the following exception:
Exception in thread "Thread-2" java.lang.NullPointerException
at pressupdate.update.run(update.java:34)
I've been researching and I can't find out what i am doing wrong.