import java.io.*;
import java.net.*;
public class DownLoad{
	URL url;
	String objFile;
	long nStartPos;
	RandomAccessFile rf;
	public DownLoad(String objFile,long nStartPos) throws IOException{
		this.nStartPos=nStartPos;
		this.objFile=objFile;
		rf=new RandomAccessFile(objFile,"rw");	
		rf.seek(nStartPos);
	}//實現下載功能
	public synchronized int write(byte[] b,int nStart,int len){
		int n=-1;
		try{
			rf.write(b,nStart,len);
			n=len;
		}catch(IOException ioe){
			ioe.printStackTrace();
		}
		return n;
	}
	public void close()throws IOException{
		rf.close();
	}
}