java的FTP工具类

以下是一个Java的FTP工具类的示例代码：

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

import java.io.*;

public class FTPUtil {
    private FTPClient ftpClient;

    public FTPUtil() {
        ftpClient = new FTPClient();
    }

    public boolean connect(String server, int port, String user, String password) {
        try {
            ftpClient.connect(server, port);
            int replyCode = ftpClient.getReplyCode();
            if (!FTPReply.isPositiveCompletion(replyCode)) {
                return false;
            }
            boolean success = ftpClient.login(user, password);
            if (!success) {
                return false;
            }
            ftpClient.setFileType(FTP.BINARY_FILE_TYPE);
            ftpClient.enterLocalPassiveMode();
            return true;
        } catch (IOException e) {
            e.printStackTrace();
            return false;
        }
    }

    public boolean uploadFile(String localFilePath, String remoteFilePath) {
        try (InputStream inputStream = new FileInputStream(localFilePath)) {
            return ftpClient.storeFile(remoteFilePath, inputStream);
        } catch (IOException e) {
            e.printStackTrace();
            return false;
        }
    }

    public boolean downloadFile(String remoteFilePath, String localFilePath) {
        try (OutputStream outputStream = new FileOutputStream(localFilePath)) {
            return ftpClient.retrieveFile(remoteFilePath, outputStream);
        } catch (IOException e) {
            e.printStackTrace();
            return false;
        }
    }

    public boolean disconnect() {
        try {
            ftpClient.logout();
            ftpClient.disconnect();
            return true;
        } catch (IOException e) {
            e.printStackTrace();
            return false;
        }
    }
}

使用该工具类，你可以连接到FTP服务器，上传文件和下载文件。你需要引入Apache Commons Net库，该库提供了FTP客户端的实现。