package com.gyarmy.testDownload;



import java.io.File;

import java.io.InputStream;

import java.io.RandomAccessFile;

import java.net.HttpURLConnection;

import java.net.MalformedURLException;

import java.net.URL;

import java.net.URLConnection;



public class ThreadDownload {

	

	private static int ThreadCount=5;

	private static String  path = "http://www.xxxx.com/file.txt";

	

	public static void main(String[] args) {

		

		try {

			URL url = new URL(path);

			HttpURLConnection conn = (HttpURLConnection)url.openConnection();

			conn.setConnectTimeout(20000);

			conn.setRequestMethod("GET");

			

			int code = conn.getResponseCode();

			if(200 == code){

				int contentLength = conn.getContentLength();

				System.out.println("长度:" + contentLength);

				

				//创建文件

				File file = new File(getFileName(path));

				

				RandomAccessFile raf = new RandomAccessFile(file, "rw");

				raf.setLength(contentLength);

				

				raf.close();

				

				int blockSize = contentLength/ThreadCount;

				

				for(int ThreadId=0;ThreadId<ThreadCount;ThreadId++){

					int startIndex = ThreadId*blockSize;

					int endIndex = (ThreadId+1)*blockSize-1;

					if(ThreadId==ThreadCount-1){

						endIndex = contentLength-1;

					}

					

					//System.out.println("线程ID:"+ThreadId+" 下载从 "+startIndex+" 开始, 结束的位置: "+endIndex);

					new MyThreadDownload(ThreadId,startIndex,endIndex).start();

				}

			}

		}catch (Exception e) {

			// TODO Auto-generated catch block

			e.printStackTrace();

		}

		

	}

	

	private static class  MyThreadDownload extends Thread{

		private int ThreadId;

		private int startIndex;

		private int endIndex;

		

		public MyThreadDownload(int ThreadId,int startIndex,int endIndex){

			this.ThreadId = ThreadId;

			this.startIndex = startIndex;

			this.endIndex = endIndex;

		}

		

		@Override

		public void run() {

			// TODO Auto-generated method stub

			super.run();

			System.out.println("线程ID:"+ThreadId+" 开始下载从 "+startIndex+" 开始, 结束的位置: "+endIndex);

			try {

				URL url = new URL(path);

				HttpURLConnection conn = (HttpURLConnection)url.openConnection();

				conn.setConnectTimeout(2000);

				conn.setRequestMethod("GET");

				conn.setRequestProperty("range", "bytes="+startIndex+"-"+endIndex);

				int code = conn.getResponseCode();

				

				if(206 == code){

					InputStream in = conn.getInputStream();

					File file = new File(getFileName(path));

					RandomAccessFile raf = new RandomAccessFile(file, "rw");

					

					raf.seek(startIndex);

					

					int len=0;

					byte[] buffer = new byte[1024];

					while((len = in.read(buffer))>0){

						raf.write(buffer, 0, len);

					}

					

					in.close();

					raf.close();

					

					

				}

				

				System.out.println("线程ID:"+ThreadId+" 下载完毕");

				

				

				

			} catch (Exception e) {

				// TODO Auto-generated catch block

				e.printStackTrace();

			}

			

		}

		

	}

	

	

	

	

	public static String getFileName(String path)

	{

		int index = path.lastIndexOf("/");

		

		return path.substring(index+1);

	}

	

}