Currency Exchange API Java GUI

I am fairly new to programming of this level and I was wondering if someone could help me with this.

So I am trying to create a currency exchange app using Java, and I have a problem updating the values on the GUI to reflect the new value on the API. Essentially ever so often the values change and it shows on the console, however, the GUI value never updates and stays the same.

I thought ActionListener would help solve this problem but either I have not implemented it properly or I haven't googled and come up with a solution properly.

Thank you in advance for any help

Here is my code:
GUI.java

public class GUI extends JFrame {
	
	static Arb arb = new Arb();

	private JPanel contentPane;
  public static void main(String[] args) throws IOException, InterruptedException {
 		
 		ActionListener taskPerformer = new ActionListener() {
             public void actionPerformed(ActionEvent evt) {
                 try {
 					arb.runUpdate_fx("anAPI");
 				} catch (IOException e) {
 					// TODO Auto-generated catch block
 					e.printStackTrace();
 				}
             }
         };
         Timer timer = new Timer(100 ,taskPerformer);
         timer.setRepeats(true);
         timer.start();
 
         Thread.sleep(5000);
 		
 		EventQueue.invokeLater(new Runnable() {
 			public void run() {
 				try {
 					GUI frame = new GUI();
 					frame.setVisible(true);
 				} catch (Exception e) {
 					e.printStackTrace();
 				}
 			}
 		});
 	}

    public GUI() {
      setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
	  setBounds(100, 100, 1121, 765);
	  contentPane = new JPanel();
	  contentPane.setBackground(Color.BLACK);
	  contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
	  contentPane.setLayout(new BorderLayout(0, 0));
	  setContentPane(contentPane);

      JTextPane FXRate = new JTextPane();
      FXRate.setForeground(new Color(255, 255, 255));
      FXRate.setBackground(new Color(0, 0, 0));
      FXRate.setEditable(false);
      FXRate.setFont(new Font("Tahoma", Font.BOLD, 11));
      panel_1.setLayout(new FlowLayout(FlowLayout.LEADING, 5, 5));
      FXRate.setText("FX Rates\r\n\r\nEUR-AUD FX Rate: " + arb.fxEURAUD + "\r\nEUR-USD FX Rate: " + arb.fxEURUSD);
      panel_1.add(FXRate);
    }
}

Result:
EUR-AUD: 1.646659
after sometime
EUR-AUD: 1.646659

Expected Result:
EUR-AUD: 1.646659
after sometime
EUR-AUD: 1.80102

References are passed by value in Java.

JTextField textField = new JTextField();
String text = "Initial text";
textField.setText(text); // no displays "Initial text";
text = "Updated text"; // doesn't change what the panel displays
// the panel still holds a reference to the old text
textField.setText(text); // updates the reference the panel holds to your new text

In your event listener, you need to call setText with the updated string to actually make the textfield display that.

Your timer and event handler look good, but the update method only fetches new values into the Arb object; nothing takes those values and puts them into the GUI. You can do that explicitly in your event handler.after the update method returns. To enable that, you may want to make FXRate a member variable, so you can access it from the action listener.