multidownload.java~2~

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.util.List;
import java.io.File;
import java.io.FileInputStream;
import java.io.RandomAccessFile;

public class MultiDownload {
        int i=0;
        int fileMark = 0;
        DownloadUtil downUtil = new DownloadUtil();
        boolean isStop[] = new boolean[10];


        public void downProcess(String url,int byteCount,int threadNum) throws Exception{
                while(i<threadNum){
                        final int startPosition = byteCount*i;
                        final int endPosition = byteCount*(i+1);

                        File file = new File("temp_file_"+i+".temp");
                        DownThread fileThread = new DownThread(url,file,
                                        startPosition,endPosition,this,i);
                        new Thread(fileThread).start();
                        i++;
                }
        }


        public void downMulitFile(DownloadInfo downInfo) throws Exception{

            String url = downInfo.getUrl();
            int threadNum = downInfo.getThreadNum();
            String filename = downInfo.getFilename();
            int fileLength = downUtil.getFileLength(url);

            if (fileLength != -1) {
                final int byteCount = (int) (fileLength / threadNum) + 1;
                boolean stopFlag = true;
                downProcess(url, byteCount, threadNum);
                stopFlag = downUtil.isFinished(isStop);
                if (stopFlag) {
                    File file = new File(filename);
                    uniteFile(threadNum, file);
                    downInfo.setIsFinished(true);
                }
            }

        }


        public void uniteFile(int threadNum,File file) throws Exception{
                for(int i=0;i<threadNum;i++){
                        File tempfile = new File("temp_file_"+i+".temp");
                        FileInputStream fis = new FileInputStream(tempfile);
                        RandomAccessFile raf = new RandomAccessFile(file, "rw");
                        byte[] buf = new byte[1024];
                        int len = -1;
                        raf.seek((long) fileMark);

                        while ((len = fis.read(buf)) != -1) {
                                raf.write(buf, 0, len);
                                fileMark += len;
                        }

                        fis.close();
                        raf.close();
                        tempfile.delete();
                }
        }
}