Difference between String StringBuffer and StringBuilder ?

--String is immutable whereas StringBuffer and StringBuilder can change their values.
--The only difference between StringBuffer and StringBuilder is that StringBuilder is unsynchronized whereas StringBuffer is synchronized. So when the application needs to be run only in a single thread then it is better to use StringBuilder. StringBuilder is more efficient than StringBuffer.
--Criteria to choose among String, StringBuffer and StringBuilder
If your text is not going to change use a string Class because a String object is immutable.
If your text can change and will only be accessed from a single thread, use a StringBuilder because StringBuilder is unsynchronized.
If your text can changes, and will be accessed from multiple threads, use a StringBuffer because StringBuffer is synchronous.