Input reading best practices

Question

I'm curious as to what opinions people might have on this. If I'm writing a program that reads in a file line-by-line and processes each one, I'm used to doing it the old K&R C-style:
reader = new BufferedReader(new FileReader(filename));
String nextLine = null;
while((nextLine = reader.readLine()) != null) {
     // Do something
}Every so often I run my code through tools like PMD and FindBugs to see what advice they might have. And it seems as though they really don't like this construct. So, I'm wondering, is there a best-practice way to do this? Something a bit cleaner that people like to use?

Answer 1

JEisen wrote:
Tolls wrote:
>
I can see that one, though I'd have thought it was a DD (according to their docs)...you're assigning null to nextLine and then reassigning readline() to it. The null's not necessary.You know, that's what I thought, but taking the null out doesn't change the warning. (I now have just 'String nextLine;')Unless you have this code inside another block - maybe a try{} for catching the IOException, in which case you might get the DU (which I don't think is necessarily a problem - doesn't it mean you are keeping things to the smallest scope as possible - generally considered a good thing. Unless I am missing something...)
Like this:
        try
            String nextLine;
            while ((nextLine = reader.readLine()) != null)
                System.out.println(nextLine);
        catch (IOException ioe)
        }>
- Avoid assignments in operandsI tend not to do this because I'm not a fan of the "do as much in one line" school of thought...but I can read it, so I don't complain about it in review meetings if it turns up in someone elses code. Life's too short for that.I managed to clear the warnings with the following code. Somehow, I think this isn't so much better as to avoid the other way, is it?
for(String nextLine = reader.readLine(); nextLine != null; nextLine = reader.readLine()) {
if(nextLine != null) {
     // Do something
I think we are talking opinion here, but I find this for loop construct worse. I would prefer one of these (if not the one being complained about):
        String nextLine = reader.readLine();
        while (nextLine != null)
            System.out.println(nextLine);
            nextLine = reader.readLine();
        do
            nextLine = reader.readLine();
            if (nextLine != null)
                System.out.println(nextLine);
        } while (nextLine != null);The disadvantage each of these options has over the original is that you do the same thing multiple different places (either nextLine = readLine() is repeated, or the null comparison is repeated).