Re: Exception in finally block

From:

Thomas Hawtin <usenet@tackline.plus.com>

Newsgroups:

comp.lang.java.programmer

Date:

Sun, 03 Dec 2006 13:27:03 +0000

Message-ID:

<4572d064$0$8722$ed2619ec@ptn-nntp-reader02.plus.net>

Red Orchid wrote:

There is my additional view of Tom Hawtin's example. First,
the following code is a part of "BufferedWriter" source.

public void close() throws IOException {
    synchronized (lock) {
        if (out == null)
            return;
        flushBuffer();
        out.close();
        out = null; // #1.
        cb = null; //
    }
}

I think that the author of "BufferedWriter" has intention to
assign null to "out" and "cb" when "close()" is called.

Look at the code. If the flush throws an exception, the out is not
closed. In fact you can't close out at all through BufferedWriter if you
it is failing on the flush. For 1.5 and earlier you need to flush the
buffer and call close on the underlying stream. Checking the bug database:

http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6266377

(Something similar exists, and also fixed in 1.6, for BufferedOutputStream.)

But, the following code discards the intention because
"out.close()" is not called.

Who cares. We flushed the buffer. The BufferedWriter is done. All
BufferedWriter.close does extra is to make sure close closes it from
further method calls (which we are not going to do).

The method "processXX" do not guarantee the consistency
of performance.

Then it's badly designed. True exception safety comes through accepting
failure may occur at any point. So it's useless trying to write code for
each failure. Keep it simple.

Tom Hawtin