实现多线程下载，暂不支持断点续传，多线程断点续传,import java.

实现多线程下载，暂不支持断点续传，多线程断点续传,import java.

import java.io.File;import java.io.InputStream;import java.io.RandomAccessFile;import java.net.HttpURLConnection;import java.net.URL;public class DownLoad {    private String urlStr;    public DownLoad(String urlStr) {        this.urlStr = urlStr;    }    /**     * 获得下载的资源的名称     *      * @return 资源的名称     */    private String getResourceName() {        return urlStr.substring(urlStr.lastIndexOf("/") + 1);    }    /**     * 开启四个线程进行下载     */    public void doWork() {        System.out.println(getResourceName());        try {            URL url = new URL(urlStr);            HttpURLConnection conn = (HttpURLConnection) url.openConnection();            conn.connect();            if (conn.getResponseCode() == HttpURLConnection.HTTP_OK) {                int size = conn.getContentLength();                System.out.println(size);                File file = new File("./" + getResourceName());                RandomAccessFile accessFile = new RandomAccessFile(file, "rwd");                accessFile.setLength(size);                accessFile.close();                int block = (size % 4 == 0) ? (size / 4) : (size / 4 + 1);                System.out.println(block);                for (int i = 0; i < 4; i++) {                    new DownLoadThread(url, file, block, i).start();                }            }        } catch (Exception e) {            e.printStackTrace();        }    }    /**     * @param args     */    public static void main(String[] args) {        DownLoad downLoad = new DownLoad(                "http://downmini.kugou.com/Kugou2012.exe");        downLoad.doWork();    }}/** * 下载线程类 * @author zhang * */class DownLoadThread extends Thread {    private URL url; // url地址    private File file; // 下载文件    private int block; // 下载信息长度    private int threadPid; // 线程id    /**     * 构造函数     * @param url     * @param file     * @param block     * @param threadPid     */    public DownLoadThread(URL url, File file, int block, int threadPid) {        this.url = url;        this.file = file;        this.block = block;        this.threadPid = threadPid;    }    /**     * 实现下载     */    public void run() {        // 计算该线程要下载信息的范围        int startPosition = threadPid * block;         int endPosition = (threadPid + 1) * block - 1;        try {            RandomAccessFile accessFile = new RandomAccessFile(file, "rwd");            accessFile.seek(startPosition);            HttpURLConnection conn = (HttpURLConnection) url.openConnection();            conn.setRequestMethod("GET");            conn.setReadTimeout(5 * 1000);            conn.setRequestProperty("Range", "bytes=" + startPosition + "-"                    + endPosition);            InputStream in = conn.getInputStream();            byte[] buf = new byte[1024];            int len = 0;            while ((len = in.read(buf)) != -1) {                accessFile.write(buf, 0, len);             }            in.close();            accessFile.close();            System.out.println("Thread id: " + threadPid + "finished");        } catch (Exception e) {            e.printStackTrace();        }    }}//该片段来自于http://byrx.net