用多线程下载视频(Java)

博主自己写的一个多线程下载文件的小程序

/**
 * 爬虫多线程下载文件
 * 
 * @author ChenYiFan
 *
 */
public class Test {

	public static void main(String[] args) {

		try {
			String urlname = "http://219.147.83.244/695EF05563F718C926E37E9/03000A010059F1DF936FEE01233E8D995A1F67-7C9C-B63F-01CE-B5EA6252C012."
					+ "mp4?ali_redirect_domain=vali-dns.cp31.o"
					+ "tt.cibntv.net&ccode=0502&duration=62&expire=18000&"
					+ "psid=2ac4ca6e7cf55a1435d242c356b17eb2&ups_client_ne"
					+ "tip=222.168.152.224&ups_ts=1509081807&ups_userid=33"
					+ "8784644&utid=341CEpTrYAECAd6of4zTB4VO&vid=XMzExMjY0OT"
					+ "I1Mg%3D%3D&vkey=A4e308094022f9680ab63ca1076ed02c8";
			URL url = new URL(urlname);
			URLConnection conn = url.openConnection();
			int length = conn.getContentLength();
			System.out.println("length=" + length);
			// 定义线程数量
			int size = 2;
			int block = length % size == 0 ? length / size : length / size + 1;
			for (int i = 0; i < size; i++) {
				int start = i * block;
				System.out.println("block=" + block);
				int end = start + (block - 1);
				if (i == size - 1) {
					end++;
				}
				new Thread(new Thread1(start, end, url)).start();
				System.out.println("start=" + start + "end=" + end);
			}
		} catch (MalformedURLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
}

class Thread1 implements Runnable {
	private int start;
	private int end;
	private URL url;
    
	public Thread1(int start, int end, URL url) {
		super();
		this.start = start;
		this.end = end;
		this.url = url;
	}

	@Override
	public void run() {
		// TODO Auto-generated method stub
		System.out.println("下载中");
		try {
			HttpURLConnection urlconn = (HttpURLConnection) url
					.openConnection();
			urlconn.setRequestProperty("Range", "bytes=" + start + "-" + end);
			if (urlconn.getResponseCode() == 206) {
				String path = System.getProperty("user.dir") + "/src/MV.mp4";
				File file = new File(path);
				InputStream in = urlconn.getInputStream();
				byte[] b = new byte[1024];
				RandomAccessFile raf = new RandomAccessFile(file, "rw");
				raf.seek(start);
				int readcode = 0;
				while ((readcode = in.read(b)) != -1) {
					raf.write(b, 0, readcode);
				}
				raf.close();
				in.close();
				System.out.println("下载完成");
			}
		} catch (IOException e) {
			// TODO Auto-generated catch block
			System.out.println("IO异常");
		}
	}
}