纳闷一早上 浏览器能拿到的文件

我用 Java 读流字节 读不到

这是 Java 代码 网上抄的? 在我本地可以用

package com.velcro.webservice.util;

import java.io.*;
import java.net.URL;
import java.net.URLConnection;
import java.util.Date;

public class FileDownloadUtil {

    public static void urlFile(String id) throws IOException, InterruptedException {
        long begin_time = new Date().getTime();
        String urlStr = "https://www.dunan.com?id=" + id;
        final URL url = new URL(urlStr);
        URLConnection conn = url.openConnection();
        String fileName = id;
        final int fileSize = conn.getContentLength();
        final int blockSize = 1024 * 1024;
        int blockNum = fileSize / blockSize;
        if ((fileSize % blockSize) != 0) {
            blockNum += 1;
        }
        Thread[] threads = new Thread[blockNum];
        for (int i = 0; i < blockNum; i++) {
            final int index = i;
            final int finalBlockNum = blockNum;
            final String finalFileName = fileName;
            threads[i] = new Thread() {
                public void run() {
                    try {
                        URLConnection conn = url.openConnection();
                        InputStream in = conn.getInputStream();
                        int beginPoint = 0, endPoint = 0;
                        beginPoint = index * blockSize;
                        if (index < finalBlockNum - 1) {
                            endPoint = beginPoint + blockSize;
                        } else {
                            endPoint = fileSize;
                        }
                        System.out.println("起始字节数：" + beginPoint + ",结束字节数：" + endPoint);
                        File filePath = new File("E:/temp_file/");
                        if (!filePath.exists()) {
                            filePath.mkdirs();
                        }
                        FileOutputStream fos = new FileOutputStream(new File("E:/temp_file/", finalFileName + "_" + (index + 1)));
                        in.skip(beginPoint);
                        byte[] buffer = new byte[1024];
                        int count;
                        int process = beginPoint;
                        while (process < endPoint) {
                            count = in.read(buffer);
                            if (process + count >= endPoint) {
                                count = endPoint - process;
                                process = endPoint;
                            } else {
                                process += count;
                            }
                            fos.write(buffer, 0, count);
                        }
                        fos.close();
                        in.close();

                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                }
            };
            threads[i].start();
        }
        for (Thread t : threads) {
            t.join();
        }
        File filePath = new File("E:/download/");
        if (!filePath.exists()) {
            filePath.mkdirs();
        }
        FileOutputStream fos = new FileOutputStream("E:/download/" + fileName);
        for (int i = 0; i < blockNum; i++) {
            FileInputStream fis = new FileInputStream("E:/temp_file/" + fileName + "_" + (i + 1));
            byte[] buffer = new byte[1024];
            int count;
            while ((count = fis.read(buffer)) > 0) {
                fos.write(buffer, 0, count);
            }
            fis.close();
        }
        fos.close();
        long end_time = new Date().getTime();
        long seconds = (end_time - begin_time) / 1000;
        long minutes = seconds / 60;
        long second = seconds % 60;
        System.out.println("下载完成,用时：" + minutes + "分" + second + "秒");
    }
}