### Source Code for HelloWorld Example

    import java.io.*;
    import jakarta.servlet.*;
    import jakarta.servlet.http.*;

    public class HelloWorld extends HttpServlet {

        public void doGet(HttpServletRequest request, HttpServletResponse response)
        throws IOException, ServletException
        {
            response.setContentType("text/html");
            PrintWriter out = response.getWriter();
            out.println("<html>");
            out.println("<head>");
            out.println("<title>Hello World!</title>");
            out.println("</head>");
            out.println("<body>");
            out.println("<h1>Hello World!</h1>");
            out.println("</body>");
            out.println("</html>");
        }
    }