To set the session timeout for a Java web application, you can use the setMaxInactiveInterval method of the HttpSession object.

Here is an example code snippet that demonstrates how to set the session timeout to 30 minutes:

import javax.servlet.http.HttpSession;
import java.util.concurrent.TimeUnit;

HttpSession session = request.getSession(); // Get the current session
session.setMaxInactiveInterval((int) TimeUnit.MINUTES.toSeconds(30)); // Set the session timeout to 30 minutes

In this example, the getSession() method is called on the HttpServletRequest object to get the current session, and then the setMaxInactiveInterval() method is called on the HttpSession object to set the session timeout to 30 minutes. The setMaxInactiveInterval() method takes an integer argument, which represents the number of seconds that the session should be inactive before it times out.

Note that the above code uses java.util.concurrent.TimeUnit to convert minutes to seconds, but you can also directly specify the number of seconds. For example, to set the session timeout to 15 minutes, you can use:

session.setMaxInactiveInterval(15 * 60); // Set the session timeout to 15 minutes

You can add this code to the doGet() or doPost() method of a servlet, or to a filter that is applied to all requests.