java 实现FTP上传下载！

首先架设一个FTP服务器，随便使用什么服务器都行：
然后去ftp://ftp.ntu.edu.tw/Apache/commons/net/下载commons net包和ftp包。导入到您的java工程，之后代码如下：

import org.apache.commons.io.IOUtils;
import org.apache.commons.net.ftp.FTPClient;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.FileOutputStream;

public class FtpTest {
    public static void main(String[] args) {
        testUpload();
        testDownload();
    }

    /**
     * FTP上传单个文件测试
     */
    public static void testUpload() {
        FTPClient ftpClient = new FTPClient();
        FileInputStream fis = null;

        try {
            ftpClient.connect("您的ip");
            ftpClient.login("您的ftp用户名", "密码");

            File srcFile = new File("C://ftp.txt");
            fis = new FileInputStream(srcFile);
            //设置上传目录
            ftpClient.changeWorkingDirectory("/ftproot");
            ftpClient.setBufferSize(1024);
            ftpClient.setControlEncoding("GBK");
            //设置文件类型（二进制）
            ftpClient.setFileType(FTPClient.BINARY_FILE_TYPE);
            ftpClient.storeFile("hello.txt", fis);
        } catch (IOException e) {
            e.printStackTrace();
            throw new RuntimeException("FTP客户端出错！", e);
        } finally {
            IOUtils.closeQuietly(fis);
            try {
                ftpClient.disconnect();
            } catch (IOException e) {
                e.printStackTrace();
                throw new RuntimeException("关闭FTP连接发生异常！", e);
            }
        }
    }

    /**
     * FTP下载单个文件测试
     */
    public static void testDownload() {
        FTPClient ftpClient = new FTPClient();
        FileOutputStream fos = null;

        try {
            ftpClient.connect("您的ip");
            ftpClient.login("您的ftp用户名", "密码");

            String remoteFileName = "/ftproot/hello.txt";
            fos = new FileOutputStream("c:/hello.txt");

            ftpClient.setBufferSize(1024);
            //设置文件类型（二进制）
            ftpClient.setFileType(FTPClient.BINARY_FILE_TYPE);
            ftpClient.retrieveFile(remoteFileName, fos);
        } catch (IOException e) {
            e.printStackTrace();
            throw new RuntimeException("FTP客户端出错！", e);
        } finally {
            IOUtils.closeQuietly(fos);
            try {
                ftpClient.disconnect();
            } catch (IOException e) {
                e.printStackTrace();
                throw new RuntimeException("关闭FTP连接发生异常！", e);
            }
        }
    }
}