Processing a file line by line in Java

I seem to use this pattern a lot, particularly in projects without dependencies (i.e., no Guava). What’s the cleanest way to iterate through a file line by line in Java? There are a lot of examples that are pretty messy. Here’s one I keep coming back to that is nice because it uses a traditional for loop to manage things. In this case it’s not just a counter variable but instead, a more general version of the for loop where we have an initializer, while condition, and iteration statement.

public void process(Reader reader) throws IOException {
  BufferedReader bufferedReader = new BufferedReader(reader);
  for (String line = bufferedReader.readLine(); line != null; line = bufferedReader.readLine()) {
    System.out.println("Line: " + line);
That’s it. That’s about as clean as I think I can get it. Note that the argument to the method isn’t a String filename but rather a Reader object, which alleviates the need for this method to have to catch FileNotFoundException as the caller would presumably supply a FileReader or some other type of Reader.

Leave a Reply

Your email address will not be published. Required fields are marked *