To open file for writing only if it does not already exist

[Daniel Polansky]

Is there a way to open file for writing so that the opening
fails if the file already exist? This needs to be atomic
operation so that it is possible to use the file as a
semaphore. As a result, the following coding does not do:

if (!file.exist()) {
// open the file for writing
...

A similar function definitely exists for accessing files in
UN*X environments.

Thank you, Dan

[Raymond DeCampo]

Daniel Polansky wrote:

Is there a way to open file for writing so that the opening
fails if the file already exist? This needs to be atomic
operation so that it is possible to use the file as a
semaphore. As a result, the following coding does not do:

if (!file.exist()) {
// open the file for writing
...

A similar function definitely exists for accessing files in
UN*X environments.

Thank you, Dan

There is the File.createNewFile() method (JRE >= 1.2). However, the
javadoc does not recommend using it for the purpose you propose but
recommends the FileLock (JRE >= 1.4) class instead.

Ray

[Daniel Polansky]

I have tried to use FileLock, but it was a bit of pain. Do you know
of a web site containing nice example code of using FileLock? How can
I achieve what I have described in the previous message with FileLock?

By the way, FileLock does not work on Windows 95, but that's not
really a problem, because Windows 95 is not officially supported, or
at least that's what Java installer said to me. My Java program works
on Windows 95 basically fine anyway.

Regards, Dan

There is the File.createNewFile() method (JRE >= 1.2). However, the
javadoc does not recommend using it for the purpose you propose but
recommends the FileLock (JRE >= 1.4) class instead.

Ray

[Raymond DeCampo]

Daniel Polansky wrote:

I have tried to use FileLock, but it was a bit of pain. Do you know
of a web site containing nice example code of using FileLock? How can
I achieve what I have described in the previous message with FileLock?

By the way, FileLock does not work on Windows 95, but that's not
really a problem, because Windows 95 is not officially supported, or
at least that's what Java installer said to me. My Java program works
on Windows 95 basically fine anyway.

My understanding is that Microsoft no longer supports Windows 95 and
that most other vendors have followed suit.

I may have been overzealous to suggest you couldn't use
File.createNewFile() for your purpose. The javadoc only says that it is
unsuitable for file locking; perhaps it can work as a semaphore.

In any case, I only just found FileLock myself. Looking at my O'Reilly
"Java NIO" book, there is an example. You may want to buy the book or
the code may be available on their website for free.

Ray

[Phil]

It's not so much that MS doesn't support 95. They don't
support NT either. The sad thing is that these OS still
work but that vendors stopped making programs for them.

phil...
"Raymond DeCampo" <rd******@twcny.rr.com> wrote in message news:p8********************@twister.nyroc.rr.com.. .

Daniel Polansky wrote:

I have tried to use FileLock, but it was a bit of pain. Do you know
of a web site containing nice example code of using FileLock? How can
I achieve what I have described in the previous message with FileLock?

By the way, FileLock does not work on Windows 95, but that's not
really a problem, because Windows 95 is not officially supported, or
at least that's what Java installer said to me. My Java program works
on Windows 95 basically fine anyway.

My understanding is that Microsoft no longer supports Windows 95 and
that most other vendors have followed suit.

I may have been overzealous to suggest you couldn't use
File.createNewFile() for your purpose. The javadoc only says that it is
unsuitable for file locking; perhaps it can work as a semaphore.

In any case, I only just found FileLock myself. Looking at my O'Reilly
"Java NIO" book, there is an example. You may want to buy the book or
the code may be available on their website for free.

Ray