Download file from FTP Server

import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.util.ArrayList;
import java.util.List;

import org.apache.commons.net.ftp.FTPClient;
import org.apache.commons.net.ftp.FTPFile;
import org.apache.commons.net.ftp.FTPFileFilter;
import org.apache.commons.net.ftp.FTPReply;

public class FTPExample {
    private static final String FTP_SERVER_ADDRESS = "127.0.0.1";
    private static final int FTP_SERVER_PORT_NUMBER = 21;
    private static final int FTP_TIMEOUT = 60000;
    private static final int BUFFER_SIZE = 1024 * 1024 * 1;
    private static final String FTP_USERNAME = "haophong";
    private static final String FTP_PASSWORD = "1234567890";
    private static final String SLASH = "/";
    private FTPClient ftpClient;

    /**
     * main
     * 
     * @param args
     */
    public static void main(String[] args) {
        String ftpFolder = "/demo";
        String downloadFolder = "E:/ftpclient";
        String extJarFile = "jar";
        FTPExample ftpExample = new FTPExample();
        // get list file ends with (.jar) from ftp server
        List<FTPFile> listFiles = 
                ftpExample.getListFileFromFTPServer(ftpFolder, extJarFile);
        // download list file from ftp server and save to "E:/ftpclient"
        for (FTPFile ftpFile : listFiles) {
            ftpExample.downloadFTPFile(ftpFolder + SLASH + ftpFile.getName(),
                    downloadFolder + SLASH + ftpFile.getName());
        }
    }

    /**
     * using method retrieveFile(String, OutputStream) 
     * to download file from FTP Server
     * 
     * @author kienthuclaptrinh.net
     * @param ftpFilePath
     * @param downloadFilePath
     */
    private void downloadFTPFile(String ftpFilePath, String downloadFilePath) {
        System.out.println("File " + ftpFilePath + " is downloading...");
        OutputStream outputStream = null;
        boolean success = false;
        try {
            File downloadFile = new File(downloadFilePath);
            outputStream = new BufferedOutputStream(
                    new FileOutputStream(downloadFile));
            // download file from FTP Server
            ftpClient.setFileType(FTPClient.BINARY_FILE_TYPE);
            ftpClient.setBufferSize(BUFFER_SIZE);
            success = ftpClient.retrieveFile(ftpFilePath, outputStream);
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                outputStream.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        if (success) {
            System.out.println("File " + ftpFilePath 
                    + " has been downloaded successfully.");
        }
    }

    /**
     * get list from ftp server
     * 
     * @author kienthuclaptrinh.net
     * @param path
     * @return List<FTPFile>
     */
    private List<FTPFile> getListFileFromFTPServer(String path, final String ext) {
        List<FTPFile> listFiles = new ArrayList<FTPFile>();
        // connect ftp server
        connectFTPServer();
        try {
            // list file ends with "jar"
            FTPFile[] ftpFiles = ftpClient.listFiles(path, new FTPFileFilter() {
                public boolean accept(FTPFile file) {
                    return file.getName().endsWith(ext);
                }
            });
            if (ftpFiles.length > 0) {
                for (FTPFile ftpFile : ftpFiles) {
                    // add file to listFiles
                    if (ftpFile.isFile()) {
                        listFiles.add(ftpFile);
                    }
                }
            }
        } catch (IOException ex) {
            ex.printStackTrace();
        }
        return listFiles;
    }

    /**
     * connect ftp server
     * 
     * @author kienthuclaptrinh.net
     */
    private void connectFTPServer() {
        ftpClient = new FTPClient();
        try {
            System.out.println("connecting ftp server...");
            // connect to ftp server
            ftpClient.setDefaultTimeout(FTP_TIMEOUT);
            ftpClient.connect(FTP_SERVER_ADDRESS, FTP_SERVER_PORT_NUMBER);
            // run the passive mode command
            ftpClient.enterLocalPassiveMode();
            // check reply code
            if (!FTPReply.isPositiveCompletion(ftpClient.getReplyCode())) {
                disconnectFTPServer();
                throw new IOException("FTP server not respond!");
            } else {
                ftpClient.setSoTimeout(FTP_TIMEOUT);
                // login ftp server
                if (!ftpClient.login(FTP_USERNAME, FTP_PASSWORD)) {
                    throw new IOException("Username or password is incorrect!");
                }
                ftpClient.setDataTimeout(FTP_TIMEOUT);
                System.out.println("connected");
            }
        } catch (IOException ex) {
            ex.printStackTrace();
        }
    }

    /**
     * disconnect ftp server
     * 
     * @author kienthuclaptrinh.net
     */
    private void disconnectFTPServer() {
        if (ftpClient != null && ftpClient.isConnected()) {
            try {
                ftpClient.logout();
                ftpClient.disconnect();
            } catch (IOException ex) {
                ex.printStackTrace();
            }
        }
    }
}