In this link the user has answered his own question and accepted his own answer.
This is like cheating the system to gain reputation.
10 points for the accepted answer and 2 for accepting it.
What to do of such cases?
Since Stack Overflow began, it has been strongly encouraged for a user to answer their own question.
In fact, it's codified in the FAQ:
It’s also OK to ask and answer your own question.
The Official Stack Overflow blog says this:
To be crystal clear, it is not merely OK to ask and answer your own question, it is explicitly encouraged.
So in short, there is nothing wrong with that.
Bottom line — never hesitate to ask and answer your own question on any Stack Exchange site. Please do! It’s all part of our shared mission to make the internet better.
There's even an option now for users to answer their own questions: