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import org.apache.commons.net.ftp.FTP;
import org.apache.commons.net.ftp.FTPClient;

import java.io.FileOutputStream;
import java.io.IOException;

public class FTPDownloader {

    public static void main(String[] args) {
        String server = "ftp.example.com";
        String username = "username";
        String password = "password";
        String remoteFile = "/path/to/remote/file.txt";
        String localFile = "local_file.txt";

        FTPClient ftpClient = new FTPClient();
        try {
            ftpClient.connect(server);
            ftpClient.login(username, password);
            ftpClient.enterLocalPassiveMode();
            ftpClient.setFileType(FTP.BINARY_FILE_TYPE);

            FileOutputStream outputStream = new FileOutputStream(localFile);
            boolean success = ftpClient.retrieveFile(remoteFile, outputStream);
            outputStream.close();

            if (success) {
                System.out.println("File downloaded successfully!");
            } else {
                System.out.println("Failed to download file!");
            }

        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if (ftpClient.isConnected()) {
                    ftpClient.logout();
                    ftpClient.disconnect();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

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璇锋敞鎰忥紝浣犻渶瑕佺‘淇濆湪椤圭洰涓寘鍚獳pache Commons Net搴撶殑渚濊禆銆?/p>