java网络编程 多线程下载，java网络编程多线程,package mult

java网络编程 多线程下载，java网络编程多线程,package mult

package multi;import java.io.File;import java.io.InputStream;import java.io.RandomAccessFile;import java.net.HttpURLConnection;import java.net.URL;public class MultiThreadDownFile {    public static void main(String[] args) {        try {            String filePath = "http://dl_dir.qq.com/qqfile/qd/QQ2012Beta3_QQProtect2.8.exe";            int threadNum = 5;            new MultiThreadDown().down(filePath, threadNum);        } catch (Exception e) {            e.printStackTrace();        }    }}class MultiThreadDown extends Thread {    private int threadId;    private int block;    private URL url;    private File file;    public MultiThreadDown() {    }    public MultiThreadDown(int threadId, int block, URL url, File file) {        super();        this.threadId = threadId;        this.block = block;        this.url = url;        this.file = file;    }    public void down(String path, int threadNum) throws Exception {        URL url = new URL(path);        HttpURLConnection conn = (HttpURLConnection) url.openConnection();        conn.setConnectTimeout(5000);        conn.setRequestMethod("GET");        try {            if (conn.getResponseCode() == 200) {                int fileLength = conn.getContentLength();// Get the length of                                                            // NetFile                System.out.println("网络文件大小：" + fileLength);                File file = new File(getFilename(path));                RandomAccessFile raf = new RandomAccessFile(file, "rwd");                raf.setLength(fileLength);                raf.close();                // 计算每条线程的下载量                int block = fileLength % threadNum == 0 ? fileLength                        / threadNum : fileLength / threadNum + 1;                for (int threadId = 0; threadId < threadNum; threadId++) {                    new MultiThreadDown(threadId, block, url, file).start();                    System.out.println("线程" + threadId + "开始");                }            } else {                System.out.println("Connection failed.");            }        } catch (Exception e) {            System.out.println("连接失败.");            e.printStackTrace();        }    }    private String getFilename(String path) {        return path.substring(path.lastIndexOf("/") + 1);    }    @Override    public void run() {        super.run();        int start = threadId * block;// 计算线程下载的网络文件的文件位置        int end = (threadId + 1) * block - 1;// 线程的结束位置        try {            RandomAccessFile raf = new RandomAccessFile(file, "rwd");            raf.seek(start);            HttpURLConnection conn = (HttpURLConnection) url.openConnection();            conn.setConnectTimeout(5000);            conn.setRequestMethod("GET");            conn.setRequestProperty("Range", "bytes=" + start + "-" + end);            if (conn.getResponseCode() == 206) {                InputStream is = conn.getInputStream();                byte[] buf = new byte[1024];                int len = 0;                while ((len = is.read(buf)) != -1) {                    raf.write(buf, 0, len);                }                raf.close();                is.close();            }            System.out.println("第" + threadId + "线程下载完毕");        } catch (Exception e) {            e.printStackTrace();        }    }}//该片段来自于http://byrx.net