HttpURLConnection下载Demo，实测有效。

1.先上图

2.java demo

/**
 * FileName:UrlDownloadTest.java
 * @author zhanggw
 * @date 2018年1月20日 下午9:42:50
 */
package com.kenick.download;

import java.io.FileOutputStream;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;

/**
 * @ClassName UrlDownloadTest
 * @author zhanggw
 * @date 2018年1月20日 下午9:42:50
 */
public class UrlDownloadDemo {
    
    public static void main(String[] args) {
        // 资源下载地址
        String downloadURL = "http://central.maven.org/maven2/HTTPClient/HTTPClient/0.3-3/HTTPClient-0.3-3.jar";
        // 本地地址
        String localFile = "d:/temp/HTTPClient-0.3-3.jar";
        // 资源下载方法
        downFile(downloadURL,localFile);
    }
    
    public static void downFile(String downloadURL,String localFile){
        try {
            System.out.println("开始下载:"+downloadURL+"\r\n本地地址:"+localFile);
            FileOutputStream fileOutputStream = new FileOutputStream(localFile);
            String urlAddr = downloadURL;
            URL url = new URL(urlAddr);
            HttpURLConnection httpURLConnection = (HttpURLConnection)url.openConnection();
            httpURLConnection.setRequestProperty("Accept", "*/*");
            int contentLength = httpURLConnection.getContentLength();
            System.out.println("下载资源总大小:"+(contentLength/1024)+"kb");
            InputStream inputStream = httpURLConnection.getInputStream();
            
            byte[] buff = new byte[1024*1024];
            int len = 0;
            int sum = 0;
            while((len=inputStream.read(buff))!=-1){
                fileOutputStream.write(buff,0,len);
                fileOutputStream.flush();
                sum += len;
                System.out.println("已下载:"+(sum/1024)+"kb/"+(contentLength/1024)+"kb");
            }
            
            fileOutputStream.close();
            inputStream.close();
            httpURLConnection.disconnect();
            System.out.println("下载完毕:"+localFile);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}