title: json parsing data from url getting nullpointException
body: <p>Getting JSONObject from URL-Json source.</p>
  
  <pre><code>   public class source02 {
         public static void main(String[] args) {
            try {
              URL url = new  URL("http://openapi.seoul.go.kr:8088/sample/json/StationDayTrnsitNmpr/1/5/");
              InputStreamReader isr = new InputStreamReader(url.openConnection().getInputStream(), "UTF-8");
              JSONObject object = (JSONObject)JSONValue.parse(isr);
  
              JSONObject sdt = (JSONObject) object.get("StationDayTrnsitNmpr");
              System.out.println(sdt.get("list_total_count").toString());
  
          } catch (Exception e) {
              e.printStackTrace();
          }
      }
  
  }
  </code></pre>
  
  <p>and Json source</p>
  
  <pre><code>   {"StationDayTrnsitNmpr":{"list_total_count":44,"RESULT":{"CODE":"INFO-000","MESSAGE":"정상 처리되었습니다"},"row":[{"SN":"1","STATN_NM":"신도림","WKDAY":333873.0,"SATDAY":298987.0,"SUNDAY":216886.0},{"SN":"2","STATN_NM":"동대문역사문화공원","WKDAY":251049.0,"SATDAY":211456.0,"SUNDAY":150589.0},{"SN":"3","STATN_NM":"충무로","WKDAY":229882.0,"SATDAY":194865.0,"SUNDAY":142150.0},{"SN":"4","STATN_NM":"종로3가","WKDAY":224539.0,"SATDAY":196606.0,"SUNDAY":142525.0},{"SN":"5","STATN_NM":"사당","WKDAY":200985.0,"SATDAY":180230.0,"SUNDAY":134354.0}]}}
  </code></pre>
  
  <p>getting java.lang.NullPointerException
      at api.source02.main(source02.java:16)</p>