[NET-455] FTPClient listFiles(FTPFileFilter) can be faster...

• Type: Improvement
• Status: Closed
• Priority: Minor
• Resolution: Not A Problem
• Affects Version/s: 3.0.1
• Component/s: FTP
• Labels: ftpclient listFiles

Environment

all

• Assignee: Unassigned
• Reporter: Nicolas
• Created: 20/Mar/12 15:42
• Updated: 17/Apr/13 19:55
• Resolved: 27/Mar/12 13:54

Description

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 =>

files = ftpClient.listFiles("./", ftpFileFilter);

It takes about 90 seconds ...

the second one is ... nearly as simple as the first one :

FTPFile []  allFilesListed = ftpClient.listFiles();
files = FTPFileFilterWithExtension.fastFilter(ftpFileFilter, allFilesListed);

The function FTPFileFilterWithExtension.fastFilter() call the same ftpFileFilter :

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);
}

The second method is EIGHT times faster than the first one ... and I don't really understand why...