extract location of tweet from twitter

Question

if the location of a tweet is not available there is any other idea to extract location i have tried to extarct location from friends tweet but it was not successsful..if the tweet is send from a mobile we track it using geolocation but if tweet is send from a computer we could not extract it..i am using java language...i have extracted the tweets related to the query..and i extarct the location of tweet if its send from a mobile phone.but if its send from a desktop computer we are not getting the place name..