Error while Rename file in ftp folder Java

Question

Following is my code to read the file and rename it afterwards. Im using apache commons.net 3.0.1.

client.connect(localhost);
boolean login = client.login("username", "password");
if(login){
    System.out.println("login successful");
    boolean chdir = client.changeWorkingDirectory("/home/folder1/child/");
    String url = client.printWorkingDirectory();   // EDIT
    FTPFile[] result = client.listFiles(url, filter);
    if (result != null && result.length > 0) {
        for (FTPFile aFile : result) {
            try{
                String filename = aFile.getName();
                InputStream is= client.retrieveFileStream(filename);
                br = new BufferedReader(new InputStreamReader(is));
                    while((line = br.readLine()) != null){
                        System.out.println("the line is"+line);
                     }
                }
                finally{
                    if(br!=null){
                        try{
                           br.close();
                           String oldFilename =url + "/" +aFile.getName();
                           String newFilename = "PRO"+aFile.getName();
                           boolean rename = client.rename(oldFilename, newFilename);
                            if(rename){
                                    System.out.println("renamed");
                            }   
                           else{
                                    System.out.println("Error in renaming");
                                }

                          }

The file deosn't get renamed and the program prints

error in renaming files (cz boolean rename = false).

I have refereed to different examples. But all seems to show the same problem. The file is picked after filter and read without any issues.

If anyone could point to what I'm doing wrong here, that'd be very helpful.

Here, the url is String url = client.printWorkingDirectory();

I have tried with both relative path and absolute path. And giving full path only to the oldFilename and just the filname to the newFilename. Both did not work.

EDIT

Before changing the directory, the url will be / which is root. After changing the directory, the url will be /home/folder1/child/. This is the where the files exists.

Answer 1

InputStream retrieveFileStream(String remote):This method returns an InputStream which we can use to read bytes from the remote file. This method gives us more control on how to read and write the data. But there are two important points when using this method:

The method completePendingCommand() must be called afterward to finalize file transfer and check its return value to verify if the download is actually done successfully.

boolean success = ftpclient.completePendingCommand();
if (success){
        System.out.println("File #2 has been downloaded successfully.");
 }

We must close the InputStream explicitly.

is.close(); //is = InputStream

SOURCE