To use cookies in a Java web application, you can use the javax.servlet.http.Cookie class. Here is an example code snippet that demonstrates how to create a cookie and set its value:

import javax.servlet.http.Cookie;

Cookie myCookie = new Cookie("myCookieName", "myCookieValue"); // Create a new cookie
myCookie.setMaxAge(60 * 60 * 24); // Set the cookie's maximum age to 1 day (in seconds)
response.addCookie(myCookie); // Add the cookie to the response

In this example, a new Cookie object is created with the name "myCookieName" and the value "myCookieValue". The setMaxAge() method is called to set the cookie's maximum age to 1 day (in seconds). Finally, the addCookie() method is called on the HttpServletResponse object to add the cookie to the response.

To read a cookie in a subsequent request, you can use the HttpServletRequest object's getCookies() method to retrieve an array of all cookies sent in the request. Here is an example code snippet that demonstrates how to retrieve the value of a cookie:

import javax.servlet.http.Cookie;

Cookie[] cookies = request.getCookies(); // Get all cookies from the request
if (cookies != null) { // Check if any cookies were sent in the request
    for (Cookie cookie : cookies) {
        if (cookie.getName().equals("myCookieName")) { // Check if the desired cookie was sent
            String myCookieValue = cookie.getValue(); // Get the value of the cookie
            // Use the value of the cookie as desired
            break;
        }
    }
}

In this example, the getCookies() method is called on the HttpServletRequest object to retrieve an array of all cookies sent in the request. If any cookies were sent, the code loops through the array to find the cookie with the name "myCookieName". Once the desired cookie is found, its value is retrieved using the getValue() method.

Note that cookies can also be set with additional attributes such as the cookie domain, path, and secure flag. The javax.servlet.http.Cookie class provides methods for setting and getting these attributes as well.