多线程下载示例

java多线程下载示例

多线程下载，如果想要做测试，必须要修改相应的文件路径，打开服务器才可，否则会出现异常。
代码如下：

/**多线程下载**/package com.itjob;import java.io.InputStream;import java.io.RandomAccessFile;import java.net.HttpURLConnection;import java.net.URL;class DownloadThread extends Thread {    int start;    int end;    String path;    public DownloadThread(int start, int end, String path) {        this.start = start;        this.end = end;        this.path = path;    }    public void run() {        try {            URL url = new URL(path);            HttpURLConnection conn = (HttpURLConnection) url.openConnection();            conn.setConnectTimeout(5000);            conn.setRequestMethod("GET");            conn.setRequestProperty("Range", "bytes=" + start + "-" + end);            InputStream is = conn.getInputStream();            System.out.println(Thread.currentThread().getName() + "号线程负责的下载范围：" + start + "---" + end);            RandomAccessFile raf = new RandomAccessFile("c:\\aaa\\test.exe", "rw");            raf.seek(start);            byte[] b = new byte[1024];            int nRead = 0;            while((nRead = is.read(b)) != -1) {                raf.write(b, 0, nRead);            }            System.out.println(Thread.currentThread().getName() + "号线程下载完毕！");        } catch (Exception e) {            e.printStackTrace();        }    }}public class MulThreadDownload {    public static void main(String[] args) {        // TODO Auto-generated method stub        try {            String path = "http://localhost:8080/MyWebServer/qqpcmgr.exe";            URL url = new URL(path);            HttpURLConnection conn = (HttpURLConnection) url.openConnection();            conn.setConnectTimeout(5000);            conn.setRequestMethod("GET");            int length = conn.getContentLength();            System.out.println("资源总长度：" + length);            RandomAccessFile raf = new RandomAccessFile("c:\\aaa\\test.exe", "rw");            raf.setLength(length);            int blockCount = 3;                     //总的线程数量            int blockSize = length / blockCount;    //每个线性要下载的数据量            for (int i = 1; i <= blockCount; i++) {                int start = (i - 1) * blockSize;                int end = i * blockSize - 1;                if (i == blockCount) {                    end = length - 1;                }                new DownloadThread(start, end, path).start();            }            raf.close();        } catch (Exception e) {            e.printStackTrace();        }    }}