Another way of joining two lines without placing cursor to that line is:
:6,6s#\n##
Here 6 is the line number to which another line will be join. To display the line number, use :set nu
.
If we are on the cursor where the next line should be joined, then:
:s#\n##
In both cases we don't need g
like :s#\n##g
, because on one line only one \n
exist.