Http多线程下载文件

 package unit;

 import java.io.ByteArrayOutputStream;
 import java.io.File;
 import java.io.FileOutputStream;
 import java.io.InputStream;
 import java.math.BigDecimal;
 import java.net.URL;
 import java.net.URLConnection;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;

 /**
  * 文件下载
  */
 public class HttpUtils {
     static long sumContent = 0;
     static float useTime = 0;
     ArrayList<Float> speed = new ArrayList<Float>();
     public static void main(String[] args) {
         String url ="http://xcy1.xiaoshikd.com/python3.zip\r\n";
         String dirPath = "D:/111/downLoad/";
         String dirPath2 = "D:/222/downLoad/";
         String dirPath3 = "D:/333/downLoad/";
         HttpUtils.download(url, dirPath, "============");
         HttpUtils.download(url, dirPath2, "============================");
         HttpUtils.download(url, dirPath3, "==============================================");
     }

     public static void download(String url, String filePath, final String message) {
          HttpUtils.getInstance().download(url, filePath, new HttpClientDownLoadProgress() {
                 @Override
                 public void onProgress(int progress) {
                     System.out.println("download progress "+message+ progress+"%");
                 }
             });
     }

     /**
      * 最大线程池
      */
     public static final int THREAD_POOL_SIZE = 4;  

     public interface HttpClientDownLoadProgress {
         public void onProgress(int progress);
     }  

     private static HttpUtils httpClientDownload;  

     private ExecutorService downloadExcutorService;  

     private HttpUtils() {
         downloadExcutorService = Executors.newFixedThreadPool(THREAD_POOL_SIZE);
     }  

     public static HttpUtils getInstance() {
         if (httpClientDownload == null) {
             httpClientDownload = new HttpUtils();
         }
         return httpClientDownload;
     }  

     /**
      * 下载文件
      *
      * @param url
      * @param filePath
      * @param progress
      *            进度回调
      */
     public void download(final String url, final String filePath, final HttpClientDownLoadProgress progress) {
         downloadExcutorService.execute(new Runnable() {
             @Override
             public void run() {
                 httpDownloadFile(url, filePath, progress);
             }
         });
     }  

     /**
      * 下载文件
      * @param url
      * @param filePath
      */
     private void httpDownloadFile(String strUrl, String filePath, HttpClientDownLoadProgress progress) {
         try {
             long startTime = System.currentTimeMillis();
             URL url = new URL(strUrl);
             String file = url.getFile();
             String fileName = file.substring(file.lastIndexOf('/')+1);
             URLConnection conn = url.openConnection();
             InputStream is = conn.getInputStream();
             long contentLength = conn.getContentLength();
             ByteArrayOutputStream output = new ByteArrayOutputStream();
             byte[] buffer = new byte[65536];
             int r = 0;
             long totalRead = 0;
             while ((r = is.read(buffer)) > 0) {
                 output.write(buffer, 0, r);
                 totalRead += r;
                 sumContent+=r;
                 if (progress != null) {// 回调进度
                     progress.onProgress((int) (totalRead * 100 / contentLength));
                 }
             }  

             /**
              * 将下载文件写入本地
              */
             File f = new File(filePath);
             if(!f.exists()) {
                 f.mkdirs();
             }
             filePath = filePath+fileName;
             FileOutputStream fos = new FileOutputStream(filePath);
             output.writeTo(fos);
             output.flush(); 

             Long endTime = System.currentTimeMillis();
             useTime = (float)(endTime-startTime)/1000;
             getDoloadResult(sumContent, useTime);

             output.close();
             fos.close();
             is.close();
             downloadExcutorService.shutdown();
         } catch (Exception e) {
             e.printStackTrace();
             downloadExcutorService.shutdown();
         }
     }  

     public void getDoloadResult(long contentLength, float useTime) {
          System.out.println("sumContentLength： "+contentLength);
          System.out.println("useTime： "+useTime);

          float bySpead = contentLength/useTime/1024/1024;
          BigDecimal b = new BigDecimal(bySpead);
          bySpead = b.setScale(2, 4).floatValue();;
          speed.add(bySpead);
          System.out.println("avgSpeed: "+bySpead+" M/s");
          System.out.println("maxSpeed: "+Collections.max(speed)+" M/s");
     }
 }