URL url = new URL("https://i.cnblogs.com");
URL url1 = new URL(url, "EditPosts.aspx?opt=1");
System.out.println(url);//https://i.cnblogs.com
System.out.println(url1);//https://i.cnblogs.com/EditPosts.aspx?opt=1
System.out.println("URL主机名称："+url1.getHost());//URL主机名称：i.cnblogs.com
System.out.println("URL协议："+url1.getProtocol());//URL协议：https
System.out.println("URL端口："+url1.getPort());//URL端口：-1
System.out.println("URL文件路径:"+url1.getPath());//URL文件路径:/iEditPosts.aspx
System.out.println("URL查询字符串："+url1.getQuery());//URL查询字符串：opt=1
System.out.println("URL相对路径："+url1.getRef());//URL相对路径：null
System.out.println("URL文件名："+url1.getFile());//URL文件名：/EditPosts.aspx?opt=1

try {
    //创建一个URL实例
    URL url = new URL("http://www.baidu.com");
    //通过URL对象的openstream方法获取一个InputStream对象
    InputStream is = url.openStream();
    InputStreamReader isr = new InputStreamReader(is, "utf-8");
    BufferedReader br = new BufferedReader(isr);
    File bd = new File(".../index.jsp");
    PrintWriter pw = new PrintWriter(bd);
    //按行读取

获取

access_token

https://api.weixin.qq.com/cgi-bin/token?grant_type=client_credential&appid=wxd65107df4acf0a81&secret=1cc78b3caf6f7e509dbffe710b1e1cd9

        String urlNameString = "https://api.weixin.qq.com/cgi-bin/token?grant_type=client_credential&appid=wxd65107df4acf0a81&secret=1cc78b3caf6f7e509dbffe710b1e1cd9";
        URL realUrl = new URL(urlNameString);
// 打开和URL之间的连接
        URLConnection connection = realUrl.openConnection();
// 设置通用的请求属性
        connection.setRequestProperty("accept", "/*");
        connection.setRequestProperty("connection", "Keep-Alive");
        connection.setRequestProperty("user-agent",
                "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1;SV1)");
        // 建立实际的连接
        connection.connect();
        // 获取所有响应头字段
        Map<String, List<String>> map = connection.getHeaderFields();
        // 遍历所有的响应头字段
        for (String key : map.keySet()) {
            System.out.println(key + "—>" + map.get(key));

        }
        // 定义 BufferedReader输入流来读取URL的响应
        BufferedReader in = new BufferedReader(new InputStreamReader(
                connection.getInputStream()));
        String line;
        String result ="";
        while ((line = in.readLine()) != null) {
            result += line;
        }
        if (in != null) {
            in.close();
        }
       return result；

/** result 返回的json串

{
"access_token": "19_pNVNyZVX5WgtPdFarp5epawu7S-0hJTv1nvQuDJTjcUaCS_gotVa_7_-eoLhPgs2K2eKZRXuEtuONJYrW4SH3qFKhLl1-QApZ57ZqtapADJcwD6uREzmEusulyUTPHjAEAWSK",
"expires_in": 7200
}

*/

access_token

;

    String s = br.readLine();
    while(s!=null){
        pw.print(s);
        pw.flush();
        s=br.readLine();
    }
    //关闭相关资源
    pw.close();
    br.close();
    isr.close();
    is.close();
} catch (IOException e) {
    e.printStackTrace();
}