Java IO流 之 RandomAccessFile 多线程下载

http://www.verejava.com/?id=16994721196019

package com.randomaccessfile;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.io.RandomAccessFile;

public class TestThreadDownload
{
	
	public static void main(String[] args)
	{
		try
		{
			InputStream is=new FileInputStream(new File("res/raf/water.jpg"));
			long contentLength=is.available();
			
			//创建一个跟要下载的文件同大小的文件
			RandomAccessFile raf=new RandomAccessFile(new File("res/raf/new2.jpg"),"rw");
			raf.setLength(contentLength);
			raf.close();
			//计算每段要下载多长
			long earchLength=contentLength/5;
			if(contentLength%5!=0)
			{
				earchLength++;
			}
			for(int i=0;i<5;i++)
			{
				new Thread(new DownloadThread(earchLength,i)).start();
			}

		} catch (FileNotFoundException e)
		{
			e.printStackTrace();
		} catch (IOException e)
		{
			e.printStackTrace();
		}
	}
	
	static class  DownloadThread implements Runnable
	{
		private long earchLength;
		private int i;
		
		public DownloadThread(long earchLength,int i)
		{
			this.earchLength=earchLength;
			this.i=i;
		}
		@Override
		public void run()
		{
			RandomAccessFile raf=null;
			try
			{
				InputStream is=new FileInputStream(new File("res/raf/water.jpg"));
				long skip=earchLength*i;
				is.skip(skip);
				raf = new RandomAccessFile(new File("res/raf/new2.jpg"),"rw");
				raf.seek(skip);
				int l=0;
				System.out.println(raf.getFilePointer());
				while((raf.getFilePointer()<=skip+earchLength)&&((l=is.read())!=-1))
				{
					raf.write(l);
				}
			} catch (FileNotFoundException e)
			{
				e.printStackTrace();
			} catch (IOException e)
			{
				e.printStackTrace();
			}
			finally
			{
				try
				{
					raf.close();
				} catch (IOException e)
				{
					e.printStackTrace();
				}
			}
			
		}
		
	}
}

http://www.verejava.com/?id=16994721196019