Top Most In a servlet, are the method variables are shared between several threads or not

public final class SomeServlet extends HttpServlet

{

  private int instanceVariable;

  public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException

  {

    int localVariable;

    HttpSession session = request.getSession();

    String sessionVariable = session.getAttribute("SomeAttribute");

  }

}

Taking the above code block as an example, the instanceVariable will be available to any thread that makes use of the servlet. If you are just using the variable for reading, and not for any modifications, then it should be fine. You can also declare the variable as static if you wanna, and it would still be acceptable to all threads that are executing the doGet method of the servlet.

The localVariable is created for each and every single thread. This is the same for pretty much all the programming languages I have ever encountered (If anyone has seen something else, please do correct me). Each thread usually has it's own memory space, and they will allocate memory for the variable and store it within their own memory space.

As for the sessionVariable, this variable is available to any servlet to which the User visits. So, if the User were to visit another servlet, regardless of the thread coz each request will spawn it's own thread, the session variable will be available to the servlet.