Change variable values in a class without acessing it's methods?

Question

I have the following scenery, a main class with:
-ArrayList of strings.
-Class frame (with textfield and button) supposed to add strings to that Array.
Ok, in main class i set the frame to run, but how to make the frame to change the ArrayList of the main class in a easy way? What is the easiest solution and the best without hurting the paradigm?
1-One solution would be to make a method in frame that returns the string and IN MAIN CLASS add it. But is this too straightforward? Like, if i had to manage 7,8 frames that must acess 7, 8 ArrayLists of main class as well as other frames recursively (Example: main class start running frame 1, then if button1 pressed go to frame 2, if button 2 pressed get textfield and chang ArrayList)
2-Another solution would be to set all ArrayLists as static variables so i can change them freely? Is this a good paradigm?
3-Pass the own main class as parameter throughout the frames? Is it possible? If so please post a 10, 15 line code in which i could do that.
4- Put the main class as mother and all frames as son and put all arraylists as protected?
I feel like im lacking one good paradigm, it should exist some concept in which the created object could change the value of the variable passed as parameter in the class that created it.
Thank you very much.

Answer 1

Thank you for your reply Kayaman, but i think you should help me.
I tried to pass a simple variable (a string) as parameter through the constructor to one frame, like any other class.
public class TelaLogin extends javax.swing.JFrame {
String a;
public TelaLogin(String a) {
this.a=a;
initComponents();
But it returns a compilation error, maybe is something in it's main method? I didn't change it:
public static void main(String args[]) {
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
new TelaLogin().setVisible(true);
The main class has a 'new TelaLogin' that looks very suspicious. Is it that?
This looks very simple.
What must i change here? Please Kayaman help me.