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package com.dsideal.YunXiaoTools.Utils;
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import java.io.*;
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import java.net.HttpURLConnection;
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import java.net.URL;
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import java.util.concurrent.*;
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import java.nio.file.*;
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public class MultiThreadDownloader {
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private final String fileUrl;
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private final String saveDir;
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private final int threadCount;
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private final long[] progress;
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private volatile boolean isPaused = false;
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private volatile boolean isCanceled = false;
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public MultiThreadDownloader(String fileUrl, String saveDir, int threadCount) {
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this.fileUrl = fileUrl;
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this.saveDir = saveDir;
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this.threadCount = threadCount;
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this.progress = new long[threadCount];
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}
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/**
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* 开始下载
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*/
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public void download() throws Exception {
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// 获取文件大小
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HttpURLConnection conn = (HttpURLConnection) new URL(fileUrl).openConnection();
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conn.setRequestMethod("GET");
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long fileSize = conn.getContentLengthLong();
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String fileName = getFileName(conn);
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conn.disconnect();
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System.out.println("文件大小: " + formatFileSize(fileSize));
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// 创建临时文件
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String tempDir = saveDir + File.separator + fileName + ".downloading";
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Files.createDirectories(Paths.get(tempDir));
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// 计算每个线程下载的块大小
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long blockSize = fileSize / threadCount;
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CountDownLatch latch = new CountDownLatch(threadCount);
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ExecutorService executor = Executors.newFixedThreadPool(threadCount);
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// 启动下载线程
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for (int i = 0; i < threadCount; i++) {
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long startPos = i * blockSize;
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long endPos = (i == threadCount - 1) ? fileSize - 1 : (i + 1) * blockSize - 1;
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String tempFile = tempDir + File.separator + "part_" + i;
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executor.execute(new DownloadTask(i, startPos, endPos, tempFile, latch));
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}
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// 启动进度显示线程
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ScheduledExecutorService progressExecutor = Executors.newSingleThreadScheduledExecutor();
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progressExecutor.scheduleAtFixedRate(() -> {
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if (!isPaused && !isCanceled) {
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showProgress(fileSize);
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}
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}, 1, 1, TimeUnit.SECONDS);
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// 等待所有线程完成
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latch.await();
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executor.shutdown();
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progressExecutor.shutdown();
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if (!isCanceled) {
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// 合并文件
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mergeFiles(tempDir, saveDir + File.separator + fileName, threadCount);
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// 删除临时文件
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deleteDirectory(tempDir);
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System.out.println("\n下载完成: " + saveDir + File.separator + fileName);
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}
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}
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private class DownloadTask implements Runnable {
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private final int threadId;
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private final long startPos;
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private final long endPos;
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private final String tempFile;
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private final CountDownLatch latch;
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public DownloadTask(int threadId, long startPos, long endPos,
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String tempFile, CountDownLatch latch) {
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this.threadId = threadId;
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this.startPos = startPos;
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this.endPos = endPos;
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this.tempFile = tempFile;
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this.latch = latch;
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}
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@Override
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public void run() {
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try {
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// 检查断点续传
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long downloadedSize = 0;
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File temp = new File(tempFile);
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if (temp.exists()) {
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downloadedSize = temp.length();
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progress[threadId] = downloadedSize;
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}
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if (downloadedSize < (endPos - startPos + 1)) {
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HttpURLConnection conn = (HttpURLConnection) new URL(fileUrl).openConnection();
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conn.setRequestMethod("GET");
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conn.setRequestProperty("Range",
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"bytes=" + (startPos + downloadedSize) + "-" + endPos);
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try (InputStream in = conn.getInputStream();
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RandomAccessFile out = new RandomAccessFile(tempFile, "rw")) {
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out.seek(downloadedSize);
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byte[] buffer = new byte[8192];
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int len;
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while ((len = in.read(buffer)) != -1 && !isCanceled) {
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if (!isPaused) {
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out.write(buffer, 0, len);
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progress[threadId] += len;
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} else {
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Thread.sleep(1000); // 暂停时休眠
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}
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}
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}
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conn.disconnect();
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}
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} catch (Exception e) {
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e.printStackTrace();
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} finally {
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latch.countDown();
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}
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}
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}
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/**
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* 显示下载进度
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*/
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private void showProgress(long fileSize) {
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long downloaded = 0;
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for (long p : progress) {
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downloaded += p;
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}
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double progress = (double) downloaded / fileSize * 100;
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String speed = formatFileSize(downloaded / 1024) + "/s";
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System.out.printf("\r下载进度: %.2f%% [%s]", progress, speed);
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}
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/**
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* 合并文件
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*/
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private void mergeFiles(String tempDir, String targetFile, int parts) throws IOException {
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try (RandomAccessFile target = new RandomAccessFile(targetFile, "rw")) {
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byte[] buffer = new byte[8192];
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for (int i = 0; i < parts; i++) {
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String partFile = tempDir + File.separator + "part_" + i;
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try (RandomAccessFile source = new RandomAccessFile(partFile, "r")) {
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int len;
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while ((len = source.read(buffer)) != -1) {
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target.write(buffer, 0, len);
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}
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}
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}
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}
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}
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// 工具方法
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private String getFileName(HttpURLConnection conn) {
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String fileName = fileUrl.substring(fileUrl.lastIndexOf("/") + 1);
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String disposition = conn.getHeaderField("Content-Disposition");
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if (disposition != null) {
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int index = disposition.indexOf("filename=");
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if (index > 0) {
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fileName = disposition.substring(index + 9).replace("\"", "");
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}
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}
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return fileName;
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}
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private String formatFileSize(long size) {
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if (size < 1024) return size + " B";
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if (size < 1024 * 1024) return String.format("%.2f KB", size / 1024.0);
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if (size < 1024 * 1024 * 1024) return String.format("%.2f MB", size / (1024.0 * 1024));
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return String.format("%.2f GB", size / (1024.0 * 1024 * 1024));
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}
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private void deleteDirectory(String dir) {
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Path directory = Paths.get(dir);
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try {
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Files.walk(directory)
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.sorted(java.util.Comparator.reverseOrder())
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.map(Path::toFile)
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.forEach(File::delete);
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} catch (IOException e) {
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e.printStackTrace();
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}
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}
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// 控制方法
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public void pause() {
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isPaused = true;
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}
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public void resume() {
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isPaused = false;
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}
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public void cancel() {
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isCanceled = true;
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}
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}
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