如果使用的是Apache Commons FTPClient类来从FTP服务器下载文件，可能会遇到该问题。此问题由于默认情况下FTPClient使用ASCII模式而不是二进制模式加载数据而导致。

下面是一个解决该问题的示例代码：

import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import org.apache.commons.net.ftp.FTP;
import org.apache.commons.net.ftp.FTPClient;

public class FTPDownloader {

    public static void main(String[] args) {

        String server = "your_ftp_server_address";
        int port = 21;
        String user = "username";
        String pass = "password";
        String remoteFilePath = "/path/on/server/file.txt";
        String localFilePath = "/path/on/local/machine/file.txt";

        FTPClient ftpClient = new FTPClient();

        try {

            ftpClient.connect(server, port);
            ftpClient.login(user, pass);
            ftpClient.enterLocalPassiveMode();
            ftpClient.setFileType(FTP.BINARY_FILE_TYPE);

            FileOutputStream outputStream = new FileOutputStream(localFilePath);

            InputStream inputStream = ftpClient.retrieveFileStream(remoteFilePath);
            byte[] bytesArray = new byte[4096];
            int bytesRead = -1;
            while ((bytesRead = inputStream.read(bytesArray)) != -1) {
                outputStream.write(bytesArray, 0, bytesRead);
            }

            boolean complete = ftpClient.completePendingCommand();
            if (complete) {
                System.out.println("File has been downloaded successfully.");
            }

            inputStream.close();
            outputStream.close();

        } catch (IOException ex) {
            System.out.println("Error while downloading file: " + ex.getMessage());
            ex.printStackTrace();
        } finally {
            try {
                if (ftpClient.isConnected()) {
                    ftpClient.logout();
                    ftpClient.disconnect();
                }
            } catch (IOException ex) {
                ex.printStackTrace();
            }
        }
    }
}

这个示例代码使用二进制文件类型从FTP服务器下载文件，确保获取源文件中的所有字节。此外，在读取数据时，代码使用字节数组缓冲器将数据保存在内存中，由于此过程中的连续