java android 多线程上载

package xiawenquan.com;import java.io.File;import java.io.InputStream;import java.io.RandomAccessFile;import java.net.HttpURLConnection;import java.net.URL;/** * 多线程下载 * @author xiawenquan * */public class MyDownLoad {		public static void main(String[] args) {				String path = "http://gb.cri.cn/mmsource/images/2011/10/22/a817ae91a2bb48e59c40673a9694b5fb.jpg";		new MyDownLoad().download(path,3);	}	/**	 * 根据路径和线程数下载文件	 * @param path	 * @param threadSize	 */	private void download(String path, int threadSize) {		try {			URL url = new URL(path);			HttpURLConnection connection = (HttpURLConnection) url.openConnection();			connection.setReadTimeout(60*1000);			connection.setRequestMethod("GET");			if(connection.getResponseCode() == 200){				int fileLength = connection.getContentLength();				File file = new File(getFileNameByPath(path));				RandomAccessFile accessFile = new RandomAccessFile(file, "rwd");				accessFile.setLength(fileLength);				accessFile.close();				// 计算每条线程下载的数据量，如果不整除则加上1				int block = fileLength / threadSize == 0 ? fileLength / threadSize : fileLength / threadSize + 1;				for(int threadid = 0; threadid < threadSize; threadid ++){					new DownLoad(threadid,block,url,file).start();				}							}else{				System.out.println("下载失败！");			}					} catch (Exception e) {			e.printStackTrace();		}	}	/**	 * 根据路径获取文件名称	 * @param path	 * @return	 */	private String getFileNameByPath(String path) {		String fileName = path.substring(path.lastIndexOf("/" ) + 1);		return fileName;	}	// 负责下载的线程类	private class DownLoad extends Thread{		private int threadid;		private int block;		private URL url;		private File file;				public DownLoad(int threadid, int block, URL url, File file) {			this.threadid = threadid;			this.block = block;			this.url = url;			this.file = file;		}				@Override		public void run() { // TODO 这个run（）是每个线程下载的代码			try {				int start = threadid * block ; // 计算线程下载的开始位置				int end = (threadid + 1) * block - 1;// 计算线程下载的结束位置				RandomAccessFile accessFile = new RandomAccessFile(file, "rwd");				accessFile.seek(start); // seek()是使每一条线程在本地文件file中的什么位置开始写入数据				// 然后每条线程去连网				HttpURLConnection connection = (HttpURLConnection) url.openConnection();				connection.setReadTimeout(60*1000);				connection.setRequestMethod("GET");				connection.setRequestProperty("Range", "bytes=" + start + "-" + end );				if(connection.getResponseCode() == 206){ // 分段下载的返回码不是200，而是206					InputStream inputStream = connection.getInputStream(); // 获取网络返回来的数据，返回来的数据是每一条线程的下载的数据					byte buffer[] = new byte[1024];					int len = 0;					while ((len = inputStream.read(buffer)) != -1) {						accessFile.write(buffer, 0, len);					}					accessFile.close();					inputStream.close();					System.out.println("第" + (threadid + 1) + "条线程下载完成");				}			} catch (Exception e) {				e.printStackTrace();			}		}	}}