In GWT you can work easily with cookies. GWT has a class that name is Cookies , with this class you can set your values into browser cookie mechanism or get values from browser cookie this class has several static method for this purposes.
Cookies.setCookie(cookieName, cookieValue, expires);
With the above method you can set your value into browser cookie with a cookie name. you can also set a timeout for your cookie in milliseconds (expire time).
You can remove your set cookie with the removeCookie method.
Cookies.removeCookie(cookieName);
With the following method you can get the list of all set cookie.
Cookies.getCookieNames();
and finally you can get a spesific cookie with the following method.
Cookies.getCookie(cookieName);
have a nice time.