java,ftp工具类

下面是一个简单的 Java FTP 工具类，可以用于上传、下载和删除文件：

import java.io.*;
import org.apache.commons.net.ftp.*;

public class FTPClientUtil {

    private FTPClient ftpClient;

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

    public void connect(String server, int port, String username, String password) throws IOException {
        ftpClient.connect(server, port);
        ftpClient.login(username, password);
    }

    public void disconnect() throws IOException {
        ftpClient.logout();
        ftpClient.disconnect();
    }

    public void uploadFile(String localFilePath, String remoteFilePath) throws IOException {
        File localFile = new File(localFilePath);
        InputStream inputStream = new FileInputStream(localFile);
        ftpClient.storeFile(remoteFilePath, inputStream);
        inputStream.close();
    }

    public void downloadFile(String localFilePath, String remoteFilePath) throws IOException {
        OutputStream outputStream = new FileOutputStream(localFilePath);
        ftpClient.retrieveFile(remoteFilePath, outputStream);
        outputStream.close();
    }

    public void deleteFile(String remoteFilePath) throws IOException {
        ftpClient.deleteFile(remoteFilePath);
    }
}

使用示例：

FTPClientUtil ftp = new FTPClientUtil();
ftp.connect("ftp.example.com", 21, "username", "password");
ftp.uploadFile("/path/to/local/file.txt", "/path/to/remote/file.txt");
ftp.downloadFile("/path/to/local/file.txt", "/path/to/remote/file.txt");
ftp.deleteFile("/path/to/remote/file.txt");
ftp.disconnect();

需要注意的是，这个工具类依赖于 Apache Commons Net 库，需要先添加这个库的依赖。