자바 파일 의 정지점 전송 다운 로드 를 실현 합 니 다.

package com.ldw.multilthreaddownload;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.RandomAccessFile;
import java.net.HttpURLConnection;
import java.net.URL;

public class Multidownload {

	static int ThreadCount = 3;   //     
	static int finishedThread = 0;   //             
	static String path = "http://192.168.0.102:8080/QQ.exe";  //      
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		
		//  get  ，         
		try {
			URL url = new URL(path);
			HttpURLConnection conn = (HttpURLConnection) url.openConnection();
			conn.setRequestMethod("GET");
			conn.setConnectTimeout(5000);
			conn.setReadTimeout(5000);
			if(conn.getResponseCode() == 200){
				//            
				int length = conn.getContentLength();
				File file = new File("QQ.exe");
				//        
				RandomAccessFile raf = new RandomAccessFile(file, "rwd");
				//         
				raf.setLength(length);
				//  raf
				raf.close();
				//              
				
				int size = length / Multidownload.ThreadCount;
				
				for(int i = 0; i < Multidownload.ThreadCount; i ++){
					//startIndex,endIndex              
					int startIndex = i * size;
					int endIndex = (i + 1) * size - 1;
					if(i == ThreadCount - 1){
						//         ，        
						endIndex = length -1;
					}
					//System.out.println("  " + i + "      " + startIndex + " " + endIndex);
					new DownLoadThread(startIndex, endIndex, i).start();
				}
			}
		} 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(){
		//  http         
		URL url;
		try {
			File fileProgress = new File(threadId + ".txt");
			//                 ，
			if(fileProgress.exists()){
				FileInputStream fis = new FileInputStream(fileProgress);
				BufferedReader br = new BufferedReader(new InputStreamReader(fis));
				//                      ，              ，        
				startIndex += Integer.parseInt(br.readLine());
				fis.close();
			}
			System.out.println("  " + threadId + "     " + startIndex +"====" + endIndex);
			url = new URL(Multidownload.path);
			HttpURLConnection conn = (HttpURLConnection) url.openConnection();
			conn.setRequestMethod("GET");
			conn.setConnectTimeout(5000);
			conn.setReadTimeout(5000);
			//         
			conn.setRequestProperty("Range", "bytes=" + startIndex + "-" + endIndex);
			//           206
			if(conn.getResponseCode() == 206){
				//          
				InputStream is = conn.getInputStream();
				byte[] b = new byte[1024];
				int len = 0;
				int total = 0;
				//         
				File file = new File("QQ.exe");
				RandomAccessFile raf = new RandomAccessFile(file, "rwd");
				//         ，startIndex
				raf.seek(startIndex);
				while((len = is.read(b)) != -1 ){
					//          ，           
					raf.write(b, 0, len);
					total += len;
					//System.out.println("  " + threadId + "   " + total);
					
					//                 
					//File fileProgress = new File(threadId + ".txt");
					RandomAccessFile fileProgressraf = new RandomAccessFile(fileProgress, "rwd");
					//             ，                  
					fileProgressraf.write((total + "").getBytes());
					fileProgressraf.close();
					
				}
				System.out.println("  " + threadId + "      ===========================");
				raf.close();
				//          ，      
				Multidownload.finishedThread++;
				//    
				synchronized(Multidownload.path){
					if(Multidownload.finishedThread == Multidownload.ThreadCount){
						for(int i = 0; i < Multidownload.ThreadCount; i++){
							File filefinish = new File(i + ".txt");
							filefinish.delete();
							
						}
						Multidownload.finishedThread = 0;
					}
				}
			}
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		
	}
}