Java多线程分块下载文件的实现示例

URL url = new URL(fileUrl);
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
conn.setRequestMethod("HEAD");
long fileSize = conn.getContentLengthLong();

int threadCount = 4; // 线程数
long blockSize = fileSize / threadCount;

ExecutorService executor = Executors.newFixedThreadPool(threadCount);
List<Future<Boolean>> futures = new ArrayList<>();

for (int i = 0; i < threadCount; i++) {
    long startPos = i * blockSize;
    long endPos = (i == threadCount - 1) ? fileSize - 1 : (i + 1) * blockSize - 1;
    
    futures.add(executor.submit(new DownloadTask(fileUrl, startPos, endPos, i)));
}

class DownloadTask implements Callable<Boolean> {
    private String fileUrl;
    private long startPos;
    private long endPos;
    private int partNum;
    
    public DownloadTask(String fileUrl, long startPos, long endPos, int partNum) {
        // 初始化参数
    }
    
    @Override
    public Boolean call() throws Exception {
        HttpURLConnection conn = (HttpURLConnection) new URL(fileUrl).openConnection();
        conn.setRequestProperty("Range", "bytes=" + startPos + "-" + endPos);
        
        try (InputStream in = conn.getInputStream();
             RandomAccessFile out = new RandomAccessFile("part" + partNum, "rw")) {
            
            out.seek(0);
            byte[] buffer = new byte[1024 * 8];
            int len;
            while ((len = in.read(buffer)) != -1) {
                out.write(buffer, 0, len);
            }
        }
        return true;
    }
}

// 等待所有任务完成
for (Future<Boolean> future : futures) {
    future.get();
}

// 合并文件
try (OutputStream out = new FileOutputStream(outputFile)) {
    for (int i = 0; i < threadCount; i++) {
        try (InputStream in = new FileInputStream("part" + i)) {
            byte[] buffer = new byte[1024 * 8];
            int len;
            while ((len = in.read(buffer)) != -1) {
                out.write(buffer, 0, len);
            }
        }
        // 删除临时文件
        new File("part" + i).delete();
    }
}