multithreaddownload

import java.io.BufferedReader;import java.io.File;import java.io.FileInputStream;import java.io.InputStream;import java.io.InputStreamReader;import java.io.RandomAccessFile;import java.net.HttpURLConnection;import java.net.MalformedURLException;import java.net.URL;import java.security.acl.LastOwnerException;import javax.print.attribute.standard.Finishings;public class Main {    static String path = "http://192.168.1.1/test.exe";    static int threadCount = 3;    static int finishedThread = 0;    public static void main(String[] args) {        try {            URL url = new URL(path);            HttpURLConnection conn = (HttpURLConnection) url.openConnection();            conn.setRequestMethod("GET");            conn.setConnectTimeout(8000);            conn.setReadTimeout(8000);            if(conn.getResponseCode() == 200){                int length = conn.getContentLength();                //创建临时文件                File file = new File(getNameFromPath(path));                RandomAccessFile raf = new RandomAccessFile(file, "rwd");                //设置临时文件大小与目标文件一致                raf.setLength(length);                raf.close();                //计算每个线程下载区间                int size = length / threadCount;                for (int id = 0; id < threadCount; id++) {                    int startIndex = id * size;                    int endIndex = (id + 1) * size - 1;                    if(id == threadCount - 1){                        endIndex = length - 1;                    }                    System.out.println("线程" + id + "下载的区间：" + startIndex + " ~ " + endIndex);                    new DownLoadThread(id, startIndex, endIndex).start();                }            }        } catch (Exception e) {            // TODO Auto-generated catch block            e.printStackTrace();        }    }    public static String getNameFromPath(String path){        int index = path.lastIndexOf("/");        return path.substring(index + 1);    }}class DownLoadThread extends Thread{    int threadId;    int startIndex;    int endIndex;    public DownLoadThread(int threadId, int startIndex, int endIndex) {        super();        this.threadId = threadId;        this.startIndex = startIndex;        this.endIndex = endIndex;    }    @Override    public void run() {        try {            File fileProgress = new File(threadId + ".txt");            int lastProgress = 0;            if(fileProgress.exists()){                FileInputStream fis = new FileInputStream(fileProgress);                BufferedReader br = new BufferedReader(new InputStreamReader(fis));                //得到上一次下载进度                lastProgress = Integer.parseInt(br.readLine());                startIndex += lastProgress;                fis.close();            }            URL url = new URL(Main.path);            HttpURLConnection conn = (HttpURLConnection) url.openConnection();            conn.setRequestMethod("GET");            conn.setConnectTimeout(8000);            conn.setReadTimeout(8000);            //设置请求数据的区间            conn.setRequestProperty("Range", "bytes=" + startIndex + "-" + endIndex);            if(conn.getResponseCode() == 206){                InputStream is = conn.getInputStream();                byte[] b = new byte[1024];                int len = 0;                //当前下载的总进度                int total = lastProgress;                File file = new File(Main.getNameFromPath(Main.path));                RandomAccessFile raf = new RandomAccessFile(file, "rwd");                raf.seek(startIndex);                while((len = is.read(b)) != -1){                    raf.write(b, 0, len);                    total += len;                    System.out.println(threadId + "下载了：" + total);                    //创建一个进度临时文件，保存下载进度                    RandomAccessFile rafProgress = new RandomAccessFile(fileProgress, "rwd");                    rafProgress.write((total + "").getBytes());                    rafProgress.close();                }                raf.close();                System.out.println(threadId + "下载完毕------------------");                //3部分全部下载完毕，才删                Main.finishedThread++;                synchronized (Main.path) {                    if(Main.finishedThread == Main.threadCount){                        for (int i = 0; i < Main.threadCount; i++) {                            File f = new File(i + ".txt");                            f.delete();                        }                        Main.finishedThread = 0;                    }                }            }        }        catch (Exception e) {            e.printStackTrace();        }    }}