如何从JTextField只接受指定的模式？

import javax.swing.*;
import javax.swing.text.*;

public class PatternTextFieldExample {
    public static void main(String[] args) {
        JFrame frame = new JFrame("PatternTextField Example");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        JTextField textField = new JTextField(20);
        ((AbstractDocument) textField.getDocument()).setDocumentFilter(new PatternDocumentFilter("\\d+"));

        frame.getContentPane().add(textField);
        frame.pack();
        frame.setVisible(true);
    }
}

class PatternDocumentFilter extends DocumentFilter {
    private String pattern;

    public PatternDocumentFilter(String pattern) {
        this.pattern = pattern;
    }

    @Override
    public void insertString(FilterBypass fb, int offset, String text, AttributeSet attr) throws BadLocationException {
        StringBuilder builder = new StringBuilder();
        builder.append(fb.getDocument().getText(0, fb.getDocument().getLength()));
        builder.insert(offset, text);

        if (builder.toString().matches(pattern)) {
            super.insertString(fb, offset, text, attr);
        }
    }

    @Override
    public void replace(FilterBypass fb, int offset, int length, String text, AttributeSet attrs) throws BadLocationException {
        StringBuilder builder = new StringBuilder();
        builder.append(fb.getDocument().getText(0, fb.getDocument().getLength()));
        builder.replace(offset, offset + length, text);

        if (builder.toString().matches(pattern)) {
            super.replace(fb, offset, length, text, attrs);
        }
    }
}