Java多线程下载文件详解编程语言

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(); }

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