public class MultiThreadDownloader {
    private static final int THREAD_COUNT = 8; // 根據(jù)網(wǎng)絡(luò)情況調(diào)整
    
    public void download(String fileUrl, String savePath) throws Exception {
        long fileSize = getFileSize(fileUrl);
        long blockSize = fileSize / THREAD_COUNT;
        
        ExecutorService executor = Executors.newFixedThreadPool(THREAD_COUNT);
        List<Future<?>> futures = new ArrayList<>();
        
        for (int i = 0; i < THREAD_COUNT; i++) {
            long startPos = i * blockSize;
            long endPos = (i == THREAD_COUNT - 1) ? fileSize - 1 : (i + 1) * blockSize - 1;
            
            futures.add(executor.submit(() -> {
                downloadBlock(fileUrl, savePath, startPos, endPos, i);
            }));
        }
        
        // 等待所有線程完成
        for (Future<?> future : futures) {
            future.get();
        }
        executor.shutdown();
        
        mergeFiles(savePath); // 合并臨時(shí)文件
    }
    
    private long getFileSize(String fileUrl) throws IOException {
        HttpURLConnection conn = (HttpURLConnection) new URL(fileUrl).openConnection();
        conn.setRequestMethod("HEAD");
        return conn.getContentLengthLong();
    }
}

public class ResumableDownloader {
    private Map<Integer, Long> progressMap = new ConcurrentHashMap<>();
    private String tempDir = "download_tmp/";
    
    public void downloadWithResume(String fileUrl, String savePath) {
        // 檢查已有進(jìn)度
        loadProgress();
        
        // 每個(gè)線程檢查自己的下載進(jìn)度
        // ... 類似多線程下載，但起始位置從progressMap中讀取
        
        // 定期保存進(jìn)度
        saveProgress();
    }
    
    private void saveProgress() {
        // 實(shí)現(xiàn)進(jìn)度保存邏輯，可以保存到文件或數(shù)據(jù)庫
    }
    
    private void loadProgress() {
        // 實(shí)現(xiàn)進(jìn)度加載邏輯
    }
}

public class FastFileWriter {
    private static final int BUFFER_SIZE = 8 * 1024; // 8KB緩沖區(qū)
    
    public void writeBlock(String path, long position, InputStream input) throws IOException {
        try (RandomAccessFile raf = new RandomAccessFile(path, "rw");
             BufferedInputStream bis = new BufferedInputStream(input, BUFFER_SIZE)) {
            
            raf.seek(position);
            byte[] buffer = new byte[BUFFER_SIZE];
            int len;
            
            while ((len = bis.read(buffer)) != -1) {
                raf.write(buffer, 0, len);
                // 更新進(jìn)度
            }
        }
    }
}

public class NetworkOptimizer {
    public static HttpURLConnection configureConnection(String url) throws IOException {
        HttpURLConnection conn = (HttpURLConnection) new URL(url).openConnection();
        
        // 重要優(yōu)化參數(shù)
        conn.setRequestProperty("Accept-Encoding", "identity"); // 禁用壓縮
        conn.setConnectTimeout(15000); // 15秒連接超時(shí)
        conn.setReadTimeout(30000);    // 30秒讀取超時(shí)
        conn.setRequestProperty("Connection", "Keep-Alive");
        conn.setRequestProperty("User-Agent", "Mozilla/5.0");
        
        return conn;
    }
}

int optimalThreads = Math.max(1, NetworkSpeedTester.getOptimalThreadCount());

MappedByteBuffer buffer = new RandomAccessFile(file, "rw")
    .getChannel()
    .map(FileChannel.MapMode.READ_WRITE, position, blockSize);

try (FileChannel destChannel = new FileOutputStream(file, true).getChannel()) {
    destChannel.transferFrom(Channels.newChannel(inputStream), position, Long.MAX_VALUE);
}

conn.setRequestProperty("Accept-Encoding", "gzip");

public class HighSpeedVideoDownloader {
    private static final String TEMP_DIR = "tmp_downloads/";
    
    public static void main(String[] args) {
        String videoUrl = "http://example.com/video.mp4";
        String savePath = "downloaded_video.mp4";
        
        try {
            new HighSpeedVideoDownloader().download(videoUrl, savePath);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    
    public void download(String fileUrl, String savePath) throws Exception {
        // 1. 創(chuàng)建臨時(shí)目錄
        createTempDir();
        
        // 2. 獲取文件信息
        long fileSize = getFileSize(fileUrl);
        int threadCount = calculateOptimalThreadCount(fileSize);
        
        // 3. 分塊下載
        downloadInParallel(fileUrl, savePath, fileSize, threadCount);
        
        // 4. 合并文件
        mergeFiles(savePath);
        
        // 5. 清理臨時(shí)文件
        cleanTempFiles();
    }
    
    // 其他具體方法實(shí)現(xiàn)...
}