StringBuffer
StringBuffer is synchronized
StringBuffer is thread-safe
StringBuffer is slow
StringBuffer is mutable
StringBuilder
StringBuilder is not synchronized
StringBuilder is not thread-safe
StringBuilder performance is better than StringBuffer
StringBuilder is mutable
https://stackoverflow.com/questions/355089/difference-between-stringbuilder-and-stringbuffer
http://www.ewdna.com/2009/06/stringbuilderstringbuffer.html