如何在 Java 中使用 SFTP 获取目录的最新文件？

Question

I am trying to get the newest file of a directory using SFTP. The below code gives the correct newest file when there is only one file in the directory. If a new file is created in the directory after some time, If I run the below code again its not giving correct newest file, its returning the same old file.(to run the below code I am using timer Scheduler).

//to have List of all the files of particular directory
List<File> files1 = new ArrayList<File>();  
Vector<LsEntry> files = sftpChannel.ls(filePath+"*.csv");

for (LsEntry entry : files)
  {
      if (!entry.getFilename().equals(".") && !entry.getFilename().equals(".."))
      {

       File f=new File(entry.getFilename());
      files1.add(f);

      }
  }  

System.out.println("files length "+files1.size());
File[] files2=files1.toArray(new File[files1.size()]);  
long lastMod = Long.MIN_VALUE;
File choice = null;
for (File file : files2) {
    if (file.lastModified() > lastMod) {
        choice = file;
        lastMod = file.lastModified();
    }
}
lastModifiedFile=choice;

I even tried using below code. It is also not giving the correct newest file.

if (files2.length > 0) {
    //** The newest file comes first 
    Arrays.sort(files2, LastModifiedFileComparator.LASTMODIFIED_REVERSE);
    lastModifiedFile = files2[0];
}

Answer 1

It could be done with Collections or stream since Vector.class is fully competible with Java-Collections:

Vector<LsEntry> list = channelSftp.ls(filePath + "*.csv");
ChannelSftp.LsEntry lastModifiedEntry = Collections.max(list,
    (Comparator.comparingInt(entry-> entry.getAttrs().getMTime()))
);

Or

LsEntry lastModifiedEntry = list.stream().max(
    Comparator.comparingInt(entry -> entry.getAttrs().getMTime())
).get();

Answer 2

Use LsEntry.getAttrs().getMTime() to query modification time of a file on SFTP server.

Vector<LsEntry> files = channelSftp.ls(filePath + "*.csv");
LsEntry newestEntry = null;
for (LsEntry entry : files)
{
    if (!entry.getFilename().equals(".") && !entry.getFilename().equals(".."))
    {
        if ((newestEntry == null) ||
            (newestEntry.getAttrs().getMTime() < entry.getAttrs().getMTime()))
        {
            newestEntry = entry;
        }
    }
}

if (newestEntry != null)
{
    System.out.println(
        "Newest file is " + newestEntry.getFilename() +
        " with timestamp " + newestEntry.getAttrs().getMtimeString());
}

---

To explain why your code does not work: You copy only file names to your File list, so the file.lastModified() cannot return any relevant value. Moreover File object is designed to work with local files only.