taskthread.java

一个简单的多线程下载程序

package com.network.flashget;

import java.io.InputStream;
import java.io.OutputStream;
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.net.*;
import java.io.RandomAccessFile;
import java.io.Serializable;

class TaskThread extends Thread implements Serializable
{
	//定义几个变量----------------------------------------------------------------------
	public long finalStart = 0;
	public long finalLength = 0;
	public long startPosition = 0;
	public long endPosition = 0;
	public String fileName = null;
	public String saveTo = null;
	public URL url = null;
	public boolean finishFlag = false;
	public long downLength = 0;
	transient public boolean stopFlag = false;
	transient public boolean destroyFlag = false;
	
	public void run()
	{
		int data = 0;
		long totalLength = endPosition - startPosition;
		BufferedInputStream bis = null;
		RandomAccessFile randomFile = null;
		System.out.println(startPosition);
		System.out.println(endPosition);
		System.out.println(totalLength);
		try
		{
			File file = new File(saveTo);
			
			//文件不存在则创建新文件--------------------------------------------------
			if (!file.exists())
			{
				System.out.println("the same file is not exist");
				file.createNewFile();
			}
			
			//创建随机读写文件--------------------------------------------------------
			randomFile = new RandomAccessFile(file,"rw");
			URLConnection urlConn = url.openConnection();
			
			//移动读写指针------------------------------------------------------------
			urlConn.setRequestProperty("RANGE", "bytes=" + startPosition+"-");			
			InputStream is = urlConn.getInputStream();
			bis = new BufferedInputStream(is);
			
			byte[] buf = new byte[1024];
			//调整指针至写的位置------------------------------------------------------
			randomFile.seek(startPosition);			

			outter:
			while(downLength < finalLength && data!=-1)
			{
				//判断该是否暂停该线程-------------------------------------------------
				try
				{
					sleep(500);
					synchronized(this)
					{
						while(stopFlag)
						{
							if(destroyFlag)
							{
								break outter;
							}
							wait();
						}
					}
				}			
				catch(InterruptedException e)
				{
					e.printStackTrace();
				} 

				//若该线程的最后读写内容不到1024字节------------------------------------
				if((finalLength - downLength) < 1023)
				{
					long len = finalLength - downLength + 1;
					data = bis.read(buf,0,(int)len);
				}
				
				else
				{
					data = bis.read(buf);
				}
				
				randomFile.write(buf,0,data);	
				downLength = downLength + data;
				startPosition = startPosition + data;		
			}
			bis.close();
			randomFile.close();
			
		}
		catch(Exception e)
		{
			e.printStackTrace();
		}
		finally
		{
			try
			{
				bis.close();
				randomFile.close();
				System.out.println(startPosition);
				System.out.println(downLength);
			}
			catch(Exception ie)
			{
				ie.printStackTrace();
			}
		}
	}
	
	//用于唤醒线程-------------------------------------------------
	public synchronized void threadNotify()
	{
		stopFlag = false;
		notify();
	}
		
}