6. What is the difference between StringBuffer and StringBuilder class? code example

Example 1: string vs stringbuilder

String is immutable and thread safe
String builder mutable and not thread safe

Example 2: 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.