叨叨两句
- 越来越难啦！干死它们！
题15: 多线程下载
package com.test;import java.io.File;import java.io.FileFilter;import java.io.FileInputStream;import java.io.FileOutputStream;import java.io.InputStream;import java.net.URL;import java.net.URLConnection;public class DownloadThread extends Thread{ //正在运行的线程个数 public static int threadCount = 0; private int startIndex; private int endIndex; private String path; private int id; public DownloadThread() { } public DownloadThread(int startIndex, int endIndex, String path, int id) { this.startIndex = startIndex; this.endIndex = endIndex; this.path = path; this.id = id; threadCount++; } public void run() { try { //创建URL对象 URL url = new URL(path); //建立连接 URLConnection conn = url.openConnection(); //配置连接 conn.setRequestProperty("Range","bytes" + startIndex + "-" + endIndex); //通过连接获取流 InputStream is = conn.getInputStream(); FileOutputStream fos = new FileOutputStream(id + ".temp"); byte[] arr = new byte[8 * 1024]; int len; while((len = is.read(arr)) != -1) { fos.write(arr, 0, len); } is.close(); fos.close(); threadCount--; System.out.println(getName() + "下载完毕"); } catch (Exception e) { e.printStackTrace(); } }}class FileUtil { public static void mergeFile(String srcPath,String destPath) throws Exception { File file = new File(srcPath); File[] subFiles = file.listFiles(new FileFilter() { public boolean accept(File pathname) { if(pathname.isFile() && pathname.getName().endsWith(".temp")) { return true; } return false; } }); FileOutputStream fos = new FileOutputStream(destPath); for (File subFile : subFiles) { FileInputStream fis = new FileInputStream(subFile); byte[] arr = new byte[8 * 1024]; int len; while((len = fis.read(arr)) != -1) { fos.write(arr, 0, len); } fis.close(); } fos.close(); System.out.println("合并完毕"); }}class ServerUtils { public static int getFileLength(String path) { try { URL url = new URL(path); URLConnection conn = url.openConnection(); int fileLength = conn.getContentLength(); return fileLength; } catch(Exception e) { return -1; } }} package com.test;public class Test05 { public static void main(String[] args) throws Exception { String path = "http://ox4j4dsnp.bkt.clouddn.com/17-10-1/58878601.jpg"; int length = ServerUtils.getFileLength(path); int count = 6; int perLength = length / count; for(int i = 0; i < count; i++) { int startIndex = perLength * i; int endIndex = perLength * (i + 1) - 1; if(i == count - 1) { endIndex = length - 1; System.out.println(endIndex); } new DownloadThread(startIndex, endIndex, path, i).start(); } while(DownloadThread.threadCount > 0) { Thread.sleep(20); } FileUtil.mergeFile("D:\\workspace\\test","D:\\workspace\\test\\copy.jpg"); }}