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
";
        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");
    }
}