import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.*;
import java.nio.charset.Charset;

public class Main extends HttpServlet {
  @Override
  protected void doGet(HttpServletRequest req, HttpServletResponse resp)
      throws ServletException, IOException {
    //resp.getWriter().print("Hello from Java! Charset: " + Charset.defaultCharset());
    resp.sendRedirect("/html/index.html");
  }
}

@@ -384,16 +384,18 @@
 ));%0A    
+//
 resp.sen
@@ -425,14 +425,177 @@
 html%22);%0A
+     RequestDispatcher view = req.getRequestDispatcher(%22/html/index.html%22);%0A        // don't add your web-app name to the path%0A%0A        view.forward(req, resp);  %0A
   %7D%0A%7D%0A

Update Main.java