File iterator

General Discussions
#1

Does anyone know, why the File class doesn’t provide an iterator method? To loop all the files in a folder I have to use the listFiles() method. Of course I can pass in a FileFilter. But it still seems more efficient to me, if I could get a file iterator from the folder. Theoretically for very large folders it would take a lot of memory and takes unnecessary time to allocate and fill the array. Additionally the listFiles() method first reads a full array of filenames and then derives a File array from it. This is doubly inefficient. And I guess, the code also creates something like an ArrayList, which has to recreate the uderlying array again and again when it is filled.

This is all fine, if I need the files as an array. But if I needs them in a different container or just want to loop over them, this seems to be dumb.

How can I effectively suggest this to Oracle?

Marvin

#2

Based on what? Actual profiler output? Or random guesswork?

Since anything file system related will almost certainly have to go via the host OS, it’s entirely likely that a single listDirContents call is much more efficient than lots of little getNextFile calls, making the actual object and array construction overhead negligible.

#3

See my implementation here:

http://www.java-gaming.org/index.php/topic,21629.0.html

FYI: list(FileFilter) and listFiles(FileFilter) do only invoke the filter when all the files have been gathered.

#4

Nice implementation. And nice coding style :). Some spaces here and there and it is perfect ;).

So Java 7 provides a way to to this out of the box?

Marvin

#5

… yes.