我如何创建一个PDF表单，然后用iText在Java中填充用户生成的数据？

import com.itextpdf.text.Document;
import com.itextpdf.text.pdf.AcroFields;
import com.itextpdf.text.pdf.PdfReader;
import com.itextpdf.text.pdf.PdfStamper;

import java.io.FileOutputStream;

public class PdfFormFiller {
    public static void main(String[] args) {
        try {
            // 1. 创建一个空白的PDF表单模板
            PdfReader reader = new PdfReader("template.pdf");
            FileOutputStream fos = new FileOutputStream("filled_form.pdf");
            PdfStamper stamper = new PdfStamper(reader, fos);
            AcroFields form = stamper.getAcroFields();

            // 2. 添加表单元素
            form.addTextField("name", "Your Name");
            form.addCheckBox("agree", "Agree", false);
            form.addRadioButton("gender", "Male", "Male", false);
            form.addRadioButton("gender", "Female", "Female", false);
            form.addComboBox("country", new String[]{"USA", "Canada", "UK"});

            // 3. 填充用户生成的数据
            form.setField("name", "John Doe");
            form.setField("agree", "Yes");
            form.setField("gender", "Male");
            form.setField("country", "USA");

            // 4. 保存填充后的PDF表单
            stamper.setFormFlattening(true);
            stamper.close();
            reader.close();
            fos.close();

            System.out.println("PDF表单填充完成！");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}