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https://issues.apache.org/jira/browse/NET-455?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13236849#comment-13236849
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Sebb commented on NET-455:
--------------------------
Does seem rather odd, because the listFiles() method actually filters the files
using FTPFileFilters.NON_NULL.
The second method should be slightly slower.
One possibility is that the FTP server (or its OS) does some caching of the
file directory listing, so that fetching the second listing is much faster than
the first.
Try repeating the test the other way around, or just repeating both methods A &
B - e.g. ABAB - in a single test.
If the behaviour really is repeatable, can you provide a simple (complete) test
case that shows the behaviour?
> FTPClient listFiles(FTPFileFilter) can be faster...
> ---------------------------------------------------
>
> Key: NET-455
> URL: https://issues.apache.org/jira/browse/NET-455
> Project: Commons Net
> Issue Type: Improvement
> Components: FTP
> Affects Versions: 3.0.1
> Environment: all
> Reporter: Nicolas
> Priority: Minor
> Labels: ftpclient, listFiles
> Original Estimate: 1h
> Remaining Estimate: 1h
>
> I tested two ways of sorting files on a remote FTP server with many files ( >
> 110 000). Both of these use the FtpFileFilter class (with a test on the
> extension filename... very simple).
> The first one is the conventionnal =>
> {code}
> files = ftpClient.listFiles("./", ftpFileFilter);
> {code}
> It takes about 90 seconds ...
> the second one is ... nearly as simple as the first one :
> {code}
> FTPFile [] allFilesListed = ftpClient.listFiles();
> files = FTPFileFilterWithExtension.fastFilter(ftpFileFilter, allFilesListed);
> {code}
> The function FTPFileFilterWithExtension.fastFilter() call the same
> ftpFileFilter :
> {code}
> public static FTPFile [] fastFilter(FTPFileFilter filter, FTPFile
> ftpFileArray []) {
> ArrayList<FTPFile> listOfFTPFiles = new ArrayList<FTPFile>();
> for (FTPFile ftpf : ftpFileArray) {
> boolean accepted = filter.accept(ftpf);
> if (accepted) {
> listOfFTPFiles.add(ftpf);
> }
> }
> FTPFile resultArray [] = new FTPFile[listOfFTPFiles.size()];
> return listOfFTPFiles.toArray(resultArray);
> }
> {code}
> The second method is EIGHT times faster than the first one ... and I don't
> really understand why...
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