Re: Closing Files that Weren't Successfully Opened

From:
Robert Klemme <shortcutter@googlemail.com>
Newsgroups:
comp.lang.java.programmer
Date:
Tue, 15 Mar 2011 06:24:36 -0700 (PDT)
Message-ID:
<bb66615a-6464-4c23-9b49-1e7e475f07f2@o10g2000vbg.googlegroups.com>
On 15 Mrz., 11:53, Michal Kleczek <klek...@gmail.com> wrote:

On Tue, 15 Mar 2011 03:41:15 -0700, Robert Klemme wrote:

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();
}


That only works because both InputStreamReader and BufferedReader
constructors don't throw.
But it is not safe to do the same for:
final ObjectInputStream ois =
  new ObjectInputStream(new FileInputStream("foo.txt"));


You just need to apply the same pattern several times:

final new FileInputStream fin = FileInputStream("foo.txt");
try {
  final ObjectInputStream ois = new ObjectInputStream(fin);
  try {
   ...
  }
  finally {
    ois.close();
  }
}
finally {
  // multiple close() do not hurt!
  fin.close();
}

Or you create a separate method for opening

private static ObjectInputStream open(String fileName) throws
IOException {
  final new FileInputStream fin = FileInputStream("foo.txt");
  boolean ok = false;
  try {
    final ObjectInputStream oin = new ObjectInputStream(fin);
    ok = true;
    return oid;
  }
  finally {
    if (!ok) fin.close();
  }
}

Or, a bit shorter:

private static ObjectInputStream open(String fileName) throws
IOException {
  final new FileInputStream fin = FileInputStream("foo.txt");
  try {
    return new ObjectInputStream(fin);
  }
  catch (IOException e) {
    fin.close();
    throw e;
  }
}

Kind regards

robert

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