You used to have
str.split(",");
and split() is a void method. It doesn’t alter str.
you could fix it by replacing str.split(",") with: str = str.split(","), or you could put it all on one line like:
while ((str = br1.readLine()) != null)
userstr.add(str.split(",")[0]);
2
solved How can I separate a single String into two parts? [duplicate]