package com.ldw.multilthreaddownload; 
 
import java.io.File; 
import java.io.InputStream; 
import java.io.RandomAccessFile; 
import java.net.HttpURLConnection; 
import java.net.URL; 
 
public class Multidownload { 
 
 static int ThreadCount = 3; //線程的個數(shù) 
 static String path = "http://192.168.0.102:8080/QQ.exe"; //確定下載地址 
 public static void main(String[] args) { 
  // TODO Auto-generated method stub 
   
  //發(fā)送get請求，請求這個地址的資源 
  try { 
   URL url = new URL(path); 
   HttpURLConnection conn = (HttpURLConnection) url.openConnection(); 
   conn.setRequestMethod("GET"); 
   conn.setConnectTimeout(5000); 
   conn.setReadTimeout(5000); 
   if(conn.getResponseCode() == 200){ 
    //獲取到請求資源文件的長度 
    int length = conn.getContentLength(); 
    File file = new File("QQ.exe"); 
    //創(chuàng)建隨機(jī)存儲文件 
    RandomAccessFile raf = new RandomAccessFile(file, "rwd"); 
    //設(shè)置臨時文件的大小 
    raf.setLength(length); 
    //關(guān)閉raf 
    raf.close(); 
    //計算出每一個線程下載多少字節(jié) 
     
    int size = length / Multidownload.ThreadCount; 
     
    for(int i = 0; i < Multidownload.ThreadCount; i ++){ 
     //startIndex,endIndex分別代表線程的開始和結(jié)束位置 
     int startIndex = i * size; 
     int endIndex = (i + 1) * size - 1; 
     if(i == ThreadCount - 1){ 
      //如果是最后一個線程，那么結(jié)束位置寫死 
      endIndex = length -1; 
     } 
     System.out.println("線程" + i + "的下載區(qū)間是" + startIndex + "到" + endIndex); 
     new DownLoadThread(startIndex, endIndex, i).start(); //創(chuàng)建線程下載數(shù)據(jù) 
    } 
   } 
  } catch (Exception e) { 
   // TODO Auto-generated catch block 
   e.printStackTrace(); 
  } 
 
 } 
 
} 
 
class DownLoadThread extends Thread{ 
 int startIndex; 
 int endIndex; 
 int threadId; 
  
 public DownLoadThread(int startIndex, int endIndex, int threadId) { 
  super(); 
  this.startIndex = startIndex; 
  this.endIndex = endIndex; 
  this.threadId = threadId; 
 } 
 
 @Override 
 public void run(){ 
  //使用http請求下載安裝包文件 
  URL url; 
  try { 
   url = new URL(Multidownload.path); 
   HttpURLConnection conn = (HttpURLConnection) url.openConnection(); 
   conn.setRequestMethod("GET"); 
   conn.setConnectTimeout(5000); 
   conn.setReadTimeout(5000); 
   //設(shè)置請求數(shù)據(jù)的區(qū)間 
   conn.setRequestProperty("Range", "bytes=" + startIndex + "-" + endIndex); 
   //請求部分?jǐn)?shù)據(jù)的響應(yīng)碼是206 
   if(conn.getResponseCode() == 206){ 
    //獲取一部分?jǐn)?shù)據(jù)來讀取 
    InputStream is = conn.getInputStream(); 
    byte[] b = new byte[1024]; 
    int len = 0; 
    int total = 0; 
    //拿到臨時文件的引用 
    File file = new File("QQ.exe"); 
    RandomAccessFile raf = new RandomAccessFile(file, "rwd"); 
    //更新文件的寫入位置，startIndex 
    raf.seek(startIndex); 
    while((len = is.read(b)) != -1 ){ 
     //每次讀取流里面的數(shù)據(jù)，同步吧數(shù)據(jù)寫入臨時文件 
     raf.write(b, 0, len); 
     total += len; 
     System.out.println("線程" + threadId + "下載了" + total); 
    } 
    System.out.println("線程" + threadId + "下載過程結(jié)束==========================="); 
    raf.close(); 
   } 
  } catch (Exception e) { 
   // TODO Auto-generated catch block 
   e.printStackTrace(); 
  } 
   
 }; 
}