Java版断点续传

功能：可以下载软件，可以下载未完成的软件
如果软件存在，则改名下载，不进行覆盖，以免勿删文件
代码如下：

import java.io.File;import java.io.IOException;import java.io.InputStream;import java.io.RandomAccessFile;import java.net.HttpURLConnection;import java.net.MalformedURLException;import java.net.URL;//断点续传public class DownLoad {    public static void down(String URL, long nPos, String savePathAndFile) {        try {            URL url = new URL(URL);            HttpURLConnection httpConnection = (HttpURLConnection) url                    .openConnection();            // 设置User-Agent            httpConnection.setRequestProperty("User-Agent", "NetFox");            // 设置断点续传的开始位置            httpConnection.setRequestProperty("RANGE", "bytes=" + nPos);            // 获得输入流            InputStream input = httpConnection.getInputStream();            RandomAccessFile oSavedFile = new RandomAccessFile(savePathAndFile,                    "rw");            // 定位文件指针到nPos位置            oSavedFile.seek(nPos);            byte[] b = new byte[1024];            int nRead;            // 从输入流中读入字节流，然后写到文件中            while ((nRead = input.read(b, 0, 1024)) > 0) {                (oSavedFile).write(b, 0, nRead);            }            httpConnection.disconnect();        } catch (MalformedURLException e) {            e.printStackTrace();        } catch (IOException e) {            e.printStackTrace();        }    }    public static long getRemoteFileSize(String url) {        long size = 0;        try {            HttpURLConnection conn = (HttpURLConnection) (new URL(url))                    .openConnection();            size = conn.getContentLength();            conn.disconnect();        } catch (Exception e) {            e.printStackTrace();        }        return size;    }public static void main(String[] args) {        String url = "http://www.videosource.cgogo.com/media/0/16/8678/8678.flv";        String savePath = "F:\\";        String fileName = url.substring(url.lastIndexOf("/"));        String fileNam=fileName;        HttpURLConnection conn = null;        try {            conn = (HttpURLConnection) (new URL(url)).openConnection();        } catch (Exception e) {            e.printStackTrace();        }        File file = new File(savePath + fileName);        // 获得远程文件大小        long remoteFileSize = getRemoteFileSize(url);        System.out.println("远程文件大小="+remoteFileSize);        int i = 0;        if (file.exists()) {            // 先看看是否是完整的，完整，换名字，跳出循环，不完整，继续下载            long localFileSize = file.length();            System.out.println("已有文件大小为:"+localFileSize);            if (localFileSize < remoteFileSize) {                System.out.println("文件续传");                down(url, localFileSize, savePath + fileName);            }else{                System.out.println("文件存在，重新下载");                do{                    i++;                    fileName = fileNam.substring(0, fileNam.indexOf(".")) + "(" + i                            + ")" + fileNam.substring(fileNam.indexOf("."));                                        file = new File(savePath + fileName);                }while(file.exists());                try {                    file.createNewFile();                } catch (IOException e) {                    e.printStackTrace();                }                down(url, 0, savePath + fileName);            }            // 下面表示文件存在，改名字                    } else {            try {                file.createNewFile();               System.out.println("下载中");                down(url, 0, savePath + fileName);            } catch (IOException e) {                e.printStackTrace();            }        }    }}