多线程下载文件及进度条java代码示例

当然，我可以为您提供一个多线程下载文件及进度条的Java代码示例。下面是一个简单的示例代码：

import java.io.BufferedInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.net.URL;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class MultiThreadedDownloader {
    private static final int BUFFER_SIZE = 4096;

    public void downloadFile(String fileUrl, String savePath, int numThreads) throws IOException {
        URL url = new URL(fileUrl);
        long fileSize = url.openConnection().getContentLengthLong();

        ExecutorService executorService = Executors.newFixedThreadPool(numThreads);
        long chunkSize = fileSize / numThreads;

        long startRange = 0;
        long endRange = chunkSize;

        for (int i = 0; i < numThreads; i++) {
            if (i == numThreads - 1) {
                endRange = fileSize; // Last thread may download slightly more than others due to rounding error
            }

            long finalStartRange = startRange;
            long finalEndRange = endRange;

            executorService.execute(() -> {
                try {
                    downloadChunk(fileUrl, savePath, finalStartRange, finalEndRange);
                } catch (IOException e) {
                    e.printStackTrace();
                }
            });

            startRange += chunkSize;
            endRange += chunkSize;
        }

        executorService.shutdown();
    }

    private void downloadChunk(String fileUrl, String savePath, long startRange, long endRange) throws IOException {
        URL url = new URL(fileUrl);
        BufferedInputStream in = new BufferedInputStream(url.openStream());
        FileOutputStream fileOutputStream = new FileOutputStream(savePath, true);

        byte[] dataBuffer = new byte[BUFFER_SIZE];
        int bytesRead;
        long downloadedBytes = 0;

        while ((bytesRead = in.read(dataBuffer, 0, BUFFER_SIZE)) != -1) {
            downloadedBytes += bytesRead;
            fileOutputStream.write(dataBuffer, 0, bytesRead);
            printProgress(downloadedBytes, startRange, endRange);
        }

        in.close();
        fileOutputStream.close();
    }

    private void printProgress(long downloadedBytes, long startRange, long endRange) {
        float progress = (float) downloadedBytes / (endRange - startRange) * 100;
        System.out.printf("Downloaded: %.2f%%\n", progress);
    }

    public static void main(String[] args) {
        MultiThreadedDownloader downloader = new MultiThreadedDownloader();

        try {
            downloader.downloadFile("http://example.com/file.zip", "save/path/file.zip", 4);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

这段代码使用多线程方式下载文件，并在控制台打印下载进度百分比。您可以将`fileUrl`替换为您要下载的文件的URL，`savePath`替换为您要保存文件的路径，`numThreads`替换为您希望使用的线程数。请确保已经引入所需的依赖和相关类。

希望这可以帮助到您！如果您有任何其他问题，请随时提问。