few = not very many, with a focus on the fact that this number is (remarkably) small.
"
a few" = not very many, but at least more than one
.
Your examples (1) and (2) are talking about the same number of friends, but (1) focuses on the fact that this is a small number and carries a negative connotation, like you don't have as many as one should/could have.
You can also have this apply to something that it is bad to have a lot of and reverse the connotations:

1. I have few enemies. (it is somewhat noteworthy how small the number is; good connotation)
2. I have a few enemies. (I don't have a large number of enemies, but I have more than one)