Java servlets can communicate with each other in various ways, such as using request dispatching, shared attributes, or session attributes. Here are some ways in which servlets can communicate with each other:

1. Request dispatching: One servlet can forward a request to another servlet or a JSP by calling the forward() or include() method on the request dispatcher. This allows the second servlet to process the request and generate a response, which is then sent back to the original servlet.

2. Shared attributes: Servlets can share data by using shared attributes. These can be set on the ServletContext, HttpSession, or HttpServletRequest objects, and can be accessed by any servlet that has access to the same object. For example, if you set an attribute on the ServletContext object in one servlet, you can access it in another servlet by calling getAttribute() on the same object.

3. Session attributes: Session attributes are specific to a user's session and can be accessed by any servlet that has access to the user's session. These can be set on the HttpSession object and can be accessed by calling getAttribute() and setAttribute() on the same object.

4. Direct HTTP communication: Servlets can communicate with each other directly using HTTP requests and responses. This is useful when the servlets are located on different servers or when they need to communicate asynchronously. For example, one servlet can send an HTTP request to another servlet and wait for the response, which can be used to update the first servlet's state.

In addition to these methods, there are also other ways in which servlets can communicate, such as using RMI or JMS. The choice of communication method depends on the specific requirements of your application and the available infrastructure.