[JAVA] "Selection does not include main type"

I'm using eclipse while learning Java. When I run code like the one below, I get the message "Selection does not include main type". Is the main type essential for code execution? The code is exactly what the school text says, but how can I do it? Thank you for your cooperation.

package la.servlet;

import java.io.IOException; import java.io.PrintWriter;

import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse;

/**

• Servlet implementation class HelloServlet */ @WebServlet("/hello") public class HelloServlet extends HttpServlet { private static final long serialVersionUID = 1L;

  /**

  • @see HttpServlet#HttpServlet() */ public HelloServlet() { super(); // TODO Auto-generated constructor stub }

  /**

  • @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response) */ protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html:charset=UTF-8"); PrintWriter out = response.getWriter(); out.println(""); out.println ("

    Welcome! To HelloServlet </ h1>"); out.println(""); }

}