如何显示（字符串）在Java GUI中的另一堂课中导致Textarea

Question

在确定输入猜测数字是否更高/较低/从大型机类中正确/正确之后，我想在FeffbackPanel类中显示字符串结果（TextArea中的TextArea位于FeftbackPanel中）。但是，在我运行代码后，相应的字符串结果未显示。在大型机类评估后，如何使用FefagbackPanel类显示字符串结果？

*我想在反馈类中的TextArea中显示的字符串结果是“恭喜，您是正确的”，“您的猜测高于目标”，“您的猜测低于目标“

反馈”类

import java.awt.BorderLayout;
import javax.swing.BorderFactory;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */

/**
 *
 * @author ThatStupidCoder
 */
public class FeedbackPanel extends JPanel{
    JTextArea ta;
        
    public FeedbackPanel(){
        setBorder(BorderFactory.createTitledBorder("Feedback"));
        setLayout(new BorderLayout());
        ta=new JTextArea(5,10);
        
        add(new JScrollPane(ta), BorderLayout.CENTER);
    }
    
    public void appendText(String text){
        ta.append(text + "\n" + "\r");
    
    }
}

Mainframe类

public class MainFrame extends JFrame{
    FeedbackPanel formPanel;
    InputPanel textPanel;
    public static int target;
    JTextArea ta;
    
    public MainFrame()
    {
    super("HIgher-Lower Game");
        
    formPanel=new FeedbackPanel();
    add(formPanel, BorderLayout.WEST);
        
        formPanel.setFormListener(new FormListener(){
            public void formEventOccurred(FormEvent e){
                int num = e.getNum();
                //int square=num*num;
                if (num == target)
                    {

                        ta.setText("Congratulations, your guess is correct!");
                        //System.out.println("Congratulations, your guess is correct!");
                    }
                else if (num > target)
                    //if guess is higher than the target
                    {
                        ta.setText("Your guess is higher than the target");
                        //System.out.println("Your guess is higher than the target");
                    }
                else if (num < target)
                    //if guess is lower than the target
                    {
                        ta.setText("Your guess is lower than the target");
                        //System.out.println("Your guess is lower than the target");
                    }
                //textPanel.appendText(Integer.toString(square));
            } 
        });
        
        textPanel=new InputPanel();
        add(textPanel, BorderLayout.EAST);
                
        setSize(300,300);
    setVisible(true);
    this.pack();
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }
     
    public static void main(String[] args) {
        Random random = new Random();
        target = random.nextInt(100);
         
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
        new MainFrame();
            }
    });
    }
}