HttpResponse中的主机名可能不为null,对于android

>我的清单文件中有Internet权限
>我在我的Url之前放了’http：//’
>我对URL进行编码

这是我的代码：

String url = "http://maps.google.com/maps/api/directions/json?origin=1600 Pennsylvania Avenue NW,Washington,DC 20500&desTination=1029 Vermont Ave NW,DC 20005&sensor=false";
   httpClient httpclient = new DefaulthttpClient();
   String goodURL = convertURL(url);//change weird characters for %etc
   httpPost httppost = new httpPost(goodURL);
   httpResponse response = httpclient.execute(httppost);

在第5行(最后一行),我的程序抛出异常.这里是确切的错误：

java.lang.IllegalArgumentexception: Host name may not be null

我在方法convertURL中编码我的字符串…

goodURL = http://maps.google.com/maps/api/directions/json?origin=3雪松大道,新泽西州高地公园08904& desTination = 604新泽西皮斯卡塔韦巴塞洛缪路604号08854& sensor = false

有什么建议么？
谢谢！