downthread.java~1~

多线程下载器。该小程序模范迅雷等下载器的下载原理实现多线程下载

package com;

/**
 * <p>Title: </p>
 *
 * <p>Description: </p>
 *
 * <p>Copyright: Copyright (c) 2009</p>
 *
 * <p>Company: </p>
 *
 * @author not attributable
 * @version 1.0
 */
import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;

public class DownThread implements Runnable{
        String url = "";
        File file;
        int startPosition;
        int endPosition;
        MultiDownload down;
        int i;

        public DownThread(String url,File file,int startPosition,int endPosition,MultiDownload down,int i){
                this.url = url;
                this.file = file;
                this.startPosition = startPosition;
                this.endPosition = endPosition;
                this.down = down;
                this.i = i;
        }

        public void run(){
                try{
                        URL downUrl = new URL(url);
                        HttpURLConnection connection = (HttpURLConnection)downUrl.openConnection();
                        InputStream is = connection.getInputStream();
                        BufferedInputStream bis = new BufferedInputStream(is);

                        FileOutputStream out = new FileOutputStream(file);
                        byte buf[] = new byte[1024];
                        int size = -1;
                        int count = 0;
                        bis.skip(startPosition+1);
                        while ((size = bis.read(buf, 0, 1024)) > 0) {
                                if ((startPosition + size) >= endPosition)
                                        size = endPosition - startPosition;
                                out.write(buf, 0, size);
                                startPosition += size;
                                count += size;
                        }
                        bis.close();
                        out.close();
                        connection.disconnect();
                }catch(Exception e){
                        e.printStackTrace();
                }
                down.isStop[i] = true;
        }
}