如何在用户输入时获取JTextField内容的长度？

import javax.swing.*;
import javax.swing.event.DocumentEvent;
import javax.swing.event.DocumentListener;

public class JTextFieldLength {
    public static void main(String[] args) {
        JFrame frame = new JFrame("JTextField Length Example");
        JTextField textField = new JTextField(20);
        JLabel label = new JLabel("字符长度: 0");

        textField.getDocument().addDocumentListener(new DocumentListener() {
            @Override
            public void insertUpdate(DocumentEvent e) {
                updateLength(e, label);
            }

            @Override
            public void removeUpdate(DocumentEvent e) {
                updateLength(e, label);
            }

            @Override
            public void changedUpdate(DocumentEvent e) {
                updateLength(e, label);
            }

            private void updateLength(DocumentEvent e, JLabel label) {
                int length = e.getDocument().getLength();
                label.setText("字符长度: " + length);
            }
        });

        frame.add(textField);
        frame.add(label);
        frame.pack();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }
}