Difference in String, StringBuilder and StringBuffer?

Since String is an immutable class every time a new String is created and older one is discarded which creates lots of temporary garbage in heap. If String are created using String literal they remain in String pool.

   To resolve this problem Java provides us two Classes StringBuffer and               StringBuilder. Both are mutable means you can  modify          StringBuffer/StringBuilder object once you created it without creating a new object.

    String Buffer is an older class but StringBuilder is relatively new and added in JDK 5. StringBuffer is very good with mutable String but it has one      disadvantage all its public methods are synchronized which makes it thread-safe but same time slow. In JDK 5 they provided similar class called    StringBuilder in Java which is a copy of StringBuffer but without synchronization