string builder and buffer code example

Example 1: stringbuilder vs stringbuffer

They both mutable, they are exactly same but
String buffer is thread safe so it runs slower
than String builder.
We are using StringBuffer when we are doing parallel
testing since it is a thread safe.

Example 2: string buffer and string builder

The StringBuffer and StringBuilder 
class both produces mutable string objects.
 The main difference between 
 them is that StringBuffer is thread safe;
 StringBuilder is not thread safe.