【fix sonar】 CASServiceUtil.java文件

jero-boot/jero-boot-module-system/src/main/java/com/jero/modules/cas/util/CASServiceUtil.java

@@ -55,12 +55,12 @@ public class CASServiceUtil {
      */
     private static String readResponse(HttpResponse response) throws IOException {
         BufferedReader in = new BufferedReader(new InputStreamReader(response.getEntity().getContent()));
-        String result = new String();
+        StringBuilder result = new StringBuilder();
         String line;
         while ((line = in.readLine()) != null) {
-            result += line;
+            result.append(line);
         }
-        return result;
+        return result.toString();
     }