gui class won't run on a different separate main file

Question

If I create a main method in my GUI class, and make an object, the program runs and works fine. However, when I try creating an object of this class in another file, the window quickly disappears.

I'm not sure why this is the case, I tried setting the frame to be visible and that doesn't work, I also tried creating a method that allows one to explicitly call the set visibility method and that didn't work either. I don't know what I'm doing wrong, any help is greatly appreciated.

import java.awt.*;
import javax.swing.*;
import java.awt.event.*;

public class BoxGUI extends JFrame{

    private JFrame frame;
    public BoxGUI(String text1, String text2) {

        //components 
        String title = "Test";
        frame = new JFrame(title);

        Container content = frame.getContentPane();
        content.setLayout(new GridLayout(0,2, 3, 4)); //Creates Grid layout 

        JTextArea leftTextArea = new JTextArea();
        leftTextArea.append("i am on the left");
        leftTextArea.append(text1);

        JTextArea rightTextArea = new JTextArea() {
            public boolean isManagingFocus() {
                return false;
            }
        };
        rightTextArea.append("i am on the right");
        rightTextArea.append(text2);

        content.add(leftTextArea);
        //leftTextArea.paste();

        content.add(rightTextArea);     
        //rightTextArea.paste();

        frame.pack();
        frame.setDefaultCloseOperation(EXIT_ON_CLOSE);// closes frame on exit 
    }

    public void displayGUI() {
        this.frame.setVisible(true);
    }
    public void CreateTextAreaComponents(String text1,String text2) {
        String title = "Test";
        frame = new JFrame(title);

        Container content = frame.getContentPane();
        content.setLayout(new GridLayout(0,2, 3, 4)); //Creates Grid layout 

        JTextArea leftTextArea = new JTextArea();
        leftTextArea.append("i am on the left");
        leftTextArea.append(text1);

        JTextArea rightTextArea = new JTextArea() {

            public boolean isManagingFocus() {
                return false;
            }
        };
        rightTextArea.append("i am on the right");
        rightTextArea.append(text2);

        content.add(leftTextArea);
        //leftTextArea.paste();

        content.add(rightTextArea);     
        //rightTextArea.paste();

        frame.pack();
        frame.setVisible(true); 
        content.setVisible(true);
        frame.setDefaultCloseOperation(EXIT_ON_CLOSE);// closes frame on exit 
    }

    public static void main (String []alex) {
        /* 
        String text1, text2;
         text1 = "\nhi, i amm on the left";
         text2 = "\nhi, i am on the right!";
         BoxGUI test = new BoxGUI(text1, text2);
         test.displayGUI();
         */
    }
}

my other file.

import javax.swing.*;
import java.util.*;
import java.io.*;

public class Project1{
    public static void main(String []args){

        String text1, text2;
        text1 = "\nhi, i amm on the left";
        text2 = "\nhi, i am on the right!";
        BoxGUI test = new BoxGUI(text1, text2);
        test.displayGUI(); 
    }
}