java.lang.ClassCastException: libcore.net.http.HttpURLConnectionImpl cannot be cast to javax.net.ssl

android 开发问题：java.lang.ClassCastException

java.lang.ClassCastException:
libcore.net.http.HttpURLConnectionImpl cannot be cast to javax.net.ssl.HttpsURLConnection

1.在虚拟器里运行时老是溢出这个异常，把自己的url从“localhost：(端口号)”改成“10.0.2.2: (端口号)”还是没用；
2.后来Google之，找到问题所在，要把’http’改成‘https’;(s代表security)
源代码：

1:  HttpsURLConnection conn = null;

2:  URL url = new URL(urlstring);

3:  conn = (HttpsURLConnection) url.openConnection(); // exception here.

logcat中爆出的异常是长这样的：

1:  06-20 15:58:05.311: E/FNF(30286): java.lang.ClassCastException: libcore.net.http.HttpURLConnectionImpl cannot be cast to javax.net.ssl.HttpsURLConnection

问题在我的import中：

1:  import javax.net.ssl.HttpsURLConnection;

解释：
SSL(Secure Sockets Layer 安全套接层)
HTTPS（Secure Hypertext Transfer Protocol）安全超文本传输协议
这两者是相互对应的。