Does fileWriter.flush() is always necessary?

[Leandro Coutinho]

Hi!

Do I always have to call flush before to close the stream?
Like:

class Writer {
	public static void main(String[] args) {
		try {
			File file = new File("newfile.txt");
			FileWriter fw = new FileWriter(file);
			fw.write("something");
			fw.flush();
			fw.close();
		} catch(IOException e) {}
	}
}

[steve souza]

Note close calls flush, so calling both is redundant. I would always call close. I'm not sure what happens in your code if an exception is thrown. It may make sense to call close in a finally clause.

http://java.sun.com/j2se/1.4.2/docs/api/java/io/Writer.html#close()

[Leandro Coutinho]

steve souza wrote:Note close calls flush, so calling both is redundant. I would always call close. I'm not sure what happens in your code if an exception is thrown. It may make sense to call close in a finally clause.

http://java.sun.com/j2se/1.4.2/docs/api/java/io/Writer.html#close()

Are you sure that close call flush? I'm reading a book that calls flush before close, and it would be redundant as you said.

[steve souza]

I'm not sure why the link below isn't going directly to the close method, but if you look at the documentation for the close method you will see it calls flush.
[url]
http://java.sun.com/j2se/1.4.2/docs/api/java/io/Writer.html#close()[/url]

[Leandro Coutinho]

steve souza wrote: I'm not sure why the link below isn't going directly to the close method, but if you look at the documentation for the close method you will see it calls flush.
[url]
http://java.sun.com/j2se/1.4.2/docs/api/java/io/Writer.html#close()[/url]

The method fw.close calls the method close from OutputStreamWriter class. Although OutputStreamWriter extends the Writer class, it overrides the close method, and its method don't call flush.

[Leandro Coutinho]

sorry.
don't mind. I was outdated.
http://java.sun.com/javase/6/docs/api/java/io/OutputStreamWriter.html

[Tim Holloway]

If you absolutely, positively HAVE to ensure it got written, call flush(). You can call flush anytime and you can call it as often as you like. If there's nothing to flush, the overhead is minimal.