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.