你作为java架构师现在需要用java实现多线程下载的实现代码

以下是使用Java实现多线程下载的示例代码：

import java.io.FileOutputStream;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;

public class MultiThreadDownloader {
    private int threadNum; // 线程数量
    private String url; // 下载链接
    private String savePath; // 保存路径
    private int fileSize; // 文件大小
    private int blockSize; // 每个线程下载的块大小

    public MultiThreadDownloader(String url, String savePath, int threadNum) {
        this.url = url;
        this.savePath = savePath;
        this.threadNum = threadNum;
    }

    // 开始下载
    public void startDownload() {
        try {
            // 获取文件大小
            fileSize = getFileSize(url);
            if (fileSize <= 0) {
                System.out.println("获取文件大小失败！");
                return;
            }

            // 计算每个线程下载的块大小
            blockSize = fileSize / threadNum;

            // 创建多个线程进行下载
            for (int i = 0; i < threadNum; i++) {
                int startPos = i * blockSize;
                int endPos = (i == threadNum - 1) ? fileSize - 1 : (i + 1) * blockSize - 1;
                new DownloadThread(i, startPos, endPos).start();
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    // 获取文件大小
    private int getFileSize(String url) throws Exception {
        int size = -1;
        HttpURLConnection conn = (HttpURLConnection) new URL(url).openConnection();
        conn.setRequestMethod("HEAD");
        conn.connect();
        if (conn.getResponseCode() == 200) {
            size = conn.getContentLength();
        }
        conn.disconnect();
        return size;
    }

    // 下载线程
    private class DownloadThread extends Thread {
        private int threadId;
        private int startPos;
        private int endPos;

        public DownloadThread(int threadId, int startPos, int endPos) {
            this.threadId = threadId;
            this.startPos = startPos;
            this.endPos = endPos;
        }

        public void run() {
            try {
                HttpURLConnection conn = (HttpURLConnection) new URL(url).openConnection();
                conn.setRequestMethod("GET");
                conn.setRequestProperty("Range", "bytes=" + startPos + "-" + endPos);
                InputStream inStream = conn.getInputStream();
                byte[] buffer = new byte[1024];
                int offset = 0;
                int length = 0;
                FileOutputStream file = new FileOutputStream(savePath, true);
                while ((length = inStream.read(buffer)) != -1) {
                    file.write(buffer, 0, length);
                    offset += length;
                }
                file.close();
                inStream.close();
                System.out.println("线程" + threadId + "下载完成！");
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }
}

使用示例：

public class Test {
    public static void main(String[] args) {
        String url = "http://example.com/sample.zip";
        String savePath = "D:/sample.zip";
        int threadNum = 5;
        MultiThreadDownloader downloader = new MultiThreadDownloader(url, savePath, threadNum);
        downloader.startDownload();
    }
}

以上代码实现了一个简单的多线程下载器，可以指定下载链接、保存路径和线程数量，然后使用多个线程同时下载文件。在实际使用中，还需要考虑异常处理、断点续传等问题