How can I access the parent's field in another class and change it?

Question

)) I'm new to Java, And I have such task:

• Create a text field component class. In the constructor, the default string must be set in the text field.
• When clicking on the field, this record should be erased.
• If user has not entered anything, and the focus from the field has been lost, then the default string should be restored. I have 3 classes: Main, MyComponent (extends JTextField), MyListener (implements MouseListener). Thats my class MyComponent:

public class MyComponent extends JTextField {
    
    private int code;
    
    public MyComponent(String text, int code) {
        super(text);
        this.code = code;
        setFont(new Font("Calibri", Font.PLAIN, 30));
}
    public int getCode() {
        return code;
    }
    
}

That's my Main:

public static void main(String[] args) {
        
        JFrame frame = new JFrame("My programm");
        frame.setBounds(320, 80, 750, 600);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        MyComponent enterName = new MyComponent("Default name", MyListener.ENTERNAME);
        enterName.addMouseListener(new MyListener());
        
        JPanel panel = new JPanel();
        JLabel labelName = new JLabel("Enter name: ");

        panel.setLayout(new GridBagLayout());
        GridBagConstraints c = new GridBagConstraints();
        c.gridx = 0;
        panel.add(labelName, c);
        c.gridx = 1;
        c.insets = new Insets(0, 10, 0, 0);
        panel.add(enterName, c);
             
        frame.add(panel);
        frame.setVisible(true); 
    }

and that's MyListener class:

public class MyListener implements MouseListener {
    
    final static public int ENTERNAME = 1;
    MyComponent enterName;

    @Override
    public void mouseClicked(MouseEvent e) {
        int code = ((MyComponent)e.getSource()).getCode();
        if (code == ENTERNAME) {
            System.out.println("Clicked on JTF"); // just to understand that MouseListener is working
             // here I need code which in String text from enterName will put "" instead of "Default name"
             }
    //...

    @Override
    public void mouseExited(MouseEvent e) {
    } 

    }

As I understand I need to make the text in the JTextField "Default name" disappear when I click the mouse. But I don't understan how should I do that. I also don't understand how to make it so that if the cursor is not on the JTextField, the default text "Default name" is returned.

I tried Reflection in MyListener, but it didn't work out well. That's my attempt:

public class MyListener implements MouseListener {
    
    final static public int ENTERNAME = 1;
    MyComponent enterName = new MyComponent("Ivan", MyListener.ENTERNAME);
    Field field = enterName.getClass().getField("text");
    field.setAccessible(true);
    
    @Override
    public void mouseClicked(MouseEvent e) {
        int code = ((MyComponent)e.getSource()).getCode();
        if (code == ENTERNAME) field.set(enterName, (String) " ");
    }

Dear Professionals, please help me! :)

Answer 1

It's much simpler than that. The class has public methods setText and getText to set/get the text. See this tutorial and the javadoc.

You dont't need reflection here, it's completely overkill and if you actually did need it, it would be a sign you were trying to do something the developers of JTextField didn't intend you to do.

It's just:

myComponent.setText("my awesome text");

My advice is that you forget you ever heard about Reflection until you are no longer "new to Java". 99% of the time you will not need it, and the 1% where you do, you should be knowing what you are doing.

In fact, that class does not even have an attribute text. Here is what setText actually does:

1377:   public void setText(String text)
1378:   {
1379:     try
1380:       {
1381:         if (doc instanceof AbstractDocument)
1382:           ((AbstractDocument) doc).replace(0, doc.getLength(), text, null);
1383:         else
1384:           {
1385:             doc.remove(0, doc.getLength());
1386:             doc.insertString(0, text, null);
1387:           }
1388:       }
1389:     catch (BadLocationException e)
1390:       {
1391:         // This can never happen.
1392:         throw (InternalError) new InternalError().initCause(e);
1393:       }
1394:   }