Re: Closing Files that Weren't Successfully Opened

From:
Robert Klemme <shortcutter@googlemail.com>
Newsgroups:
comp.lang.java.programmer
Date:
Tue, 15 Mar 2011 03:41:15 -0700 (PDT)
Message-ID:
<e20f9083-fe92-46f8-8cd4-7db4bfc426c4@p16g2000vbo.googlegroups.com>
On 15 Mrz., 08:52, Lawrence D'Oliveiro <l...@geek-
central.gen.new_zealand> wrote:

In message <4pp258-hg4....@dagon.net>, Dagon wrote:

It's not uncommon to see code like:
    finally {
        if (someResource != null) {
            try {
                someResource.close();
            } catch (exceptionsCloseCanThrow ecct) {
                logger.error("WTF!", ecct);
            }
        }
    }

This is ugly, and an admission that you haven't tracked the state of yo=

ur

resource very well ...


What's the alternative?


The alternative is to create and assign outside the block and do the
close in finally - unconditionally:

final FileInputStream fin = new FileInputStream("foo.txt");
try {
  final byte[] buffer = new byte[1024];
  for (int read;(read = fin.read(buffer))>=0;) {
    // do whatever with buffer[0,read[
  }
}
finally {
  // no null or other check needed!
  fin.close();
}

If you want to ensure an exception from close() does not shadow
another error you can do

static void close(Closable c) {
  try {
    c.close();
  }
  catch (IOException e) {
    // ignore or log
  }
}

and use that in the finally block.

If you want BufferedReader you can do

final BufferedReader reader =
  new BufferedReader(new InputStreamReader(new
FileInputStream("foo.txt")));
try {
  for (String line; (line = reader.readLine()) != null;) {
    System.out.println("Found line: " + line);
  }
}
finally {
  reader.close();
}

I would declare IOException on the method that contains this code to
leave IO error handling to callers.

Kind regards

robert

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