Simple Question Making a Variable Accessable throught the code

[2o2]

at the bottom in the public void run, i declare a jtextfield called screen. how would i then allow this variable to be used in my actionlistner class where i am trying to set the text using screen.setText?

import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JTextField;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JComponent;
import java.awt.BorderLayout;
import java.awt.Container;
import java.awt.Dimension;
import javax.swing.*; 
import java.awt.*; 
import java.awt.event.*; 
public class Simplebuttongrid
{
  private JPanel mainPanel = new JPanel(); // panel holds the button grid
  String[][] buttonStrings = // use these Strings to create a JButton grid
  {
      {"7", "8", "9", "/"},
      {"4", "5", "6", "*"},
      {"1", "2", "3", "-"},
      {"0", ".", "=", "+"},
  };

  public Simplebuttongrid()
  {
    int rowLength = buttonStrings.length;
    int colLength = buttonStrings[0].length;
    mainPanel.setLayout(new GridLayout(rowLength, colLength));
    ButtonListener buttonListener = new ButtonListener(); // create our ActionListener
    for (int row = 0; row < rowLength; row++)
    {
      for (int col = 0; col < colLength; col++)
      {
        // for each String in the array, create a button that holds the string
        String buttonString = buttonStrings[row][col];
        JButton button = new JButton(buttonString); // this button here
        button.addActionListener(buttonListener); // add the listener
        mainPanel.add(button); // and add it to the panel
      }
    }
  }

  public JComponent getComponent()
  {
    return mainPanel;
  }
  //public JComponent getComponent2()
  //{
  //	return screenPanel;
 // }
  
  // here's the button listener class that of course implements action listener
  private class ButtonListener implements ActionListener
  {
    public void actionPerformed(ActionEvent e)
    {
      // we can easily extract the String held by the button pressed 
      String actionCommand = e.getActionCommand(); // here's the string
      if (actionCommand == "5"){
      	 screen.setText("grr");  // heres where i want to be able to access the jtextfield screen
      }
     
    }
  }

  
  public static void main(String[] args)
  {
    java.awt.EventQueue.invokeLater(new Runnable()
    {
      public void run()
      {
            JFrame frame = new JFrame("Calculator"); 
   	frame.setLayout(new BorderLayout());
    //frame.getContentPane().add(new Simplebuttongrid().getComponent2());
    frame.getContentPane().add(new Simplebuttongrid().getComponent());
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.pack();
    frame.setLocationRelativeTo(null);
    frame.setVisible(true);
    //heres where i set the screen
    JTextField screen = new JTextField(13);
    JPanel screenPanel = new JPanel(); //panel to hold screen
    screenPanel.setLayout(new GridLayout(1,1));
    screenPanel.add(screen);
    frame.add(screenPanel, BorderLayout.NORTH);

      }
    });
  }
}

[Norm]

JTextField screen

Put this part outside of a method as a class variable.