import java.io.File;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.net.HttpURLConnection;
import java.net.URL;
 
public class DownloadFile {
 
    /**
     * @param args
     */
    static int len;//线程平均下载文件长度
    static int bn ;//每个线程写入文件的字节数
    static int tn; //线程数
    static String urlt;//下载地址
    static String fileName;
    static RandomAccessFile osf; //文件操作
    public static void main(String[] args) {
        // TODO Auto-generated method stub
         
        try {
            urlt = "http://192.168.16.77:8080/Stargreat/html/baidu player";
            fileName = "C:\" + urlt.split("//")[1].split("/")[urlt.split("//")[1].split("/").length-1];
            System.out.println(fileName);
            URL url = new URL(urlt);
            HttpURLConnection http = (HttpURLConnection) url.openConnection();
 
            /**
             * 此处设定5个线程下载一个文件tn = 5;
             * 判断平均每个线程需下载文件长度：
             */
            System.out.println("file size:" + http.getContentLength());
            tn = 3;         
            len = http.getContentLength() / tn ;//舍去余数（余数自动舍去）计算每个线程应下载平均长度，最后一个线程再加上余数，则是整个文件的长度,
            File f = new File(fileName);
            if (f.exists()){
                f.delete();
                osf = new RandomAccessFile(f, "rw");
                osf.seek(http.getContentLength()-1);
                osf.write(0);
            }else{
                osf = new RandomAccessFile(f, "rw");
                osf.seek(http.getContentLength()-1);
                osf.write(0);
            }
            System.out.println("temp 文件长度：" + f.length());
            Thread t;//下载子线程，
            for (int j = 0; j < tn; j++) {
                if(j == tn - 1){//如果最后一个线程则加上余数长度字节
                    bn = len + (http.getContentLength() % tn);
                }else{
                    bn = len;
                }
                System.out.println("t"+ j + "线程下载长度：" + bn + "起始字节：" + len*j);
                t = new DT(
                        j,
                        urlt,
                        fileName,
                        len*j,
                        bn
                         
                );
                t.start();
            }
 
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
 
}


//java/6863