Remove the init method and move its content to the constructor.

Using the init method outside of the constructor will lead to a memory
leak, because the 2 pointers will not be deleted.

As the method is not required, I dropped it.
It seems to be a bad habit. The `delete` operator has no effect on `NULL` value.
However, we should reset the pointers to [nullptr](http://en.cppreference.com/w/cpp/language/nullptr).