java.io.StringReader中线程“main”java.lang.NullPointerException中的异常。（未知来源）

I am trying to convert my Xml string into an json object. I am using the org.Json package. I have requested information from the wolfram alpha server. The server give back xml and i want to used the org.json package to convert it to json. The method I am trying to use is static which lies inside the XML class. I created a JSONObject method thinking that i would convert but i keep getting an error message. I am trying to convert my Xml string into an js