bug fix

distributed-print-business/src/main/java/com/qmth/distributed/print/business/util/CreatePdfUtil.java

@@ -167,19 +167,21 @@ public class CreatePdfUtil {
 //        }
 
         for (ExamStudentCourseDto e : examStudentList) {
-            char[] chars = e.getSiteNumber().toLowerCase().toCharArray();
-            String ascii = "";
-            for (int i = 0; i < chars.length; i++) {
-                ascii = ascii + chars[i];
+            if (Objects.nonNull(e.getSiteNumber()) && Objects.equals(e.getSiteNumber(), "")) {
+                char[] chars = e.getSiteNumber().toLowerCase().toCharArray();
+                String ascii = "";
+                for (int i = 0; i < chars.length; i++) {
+                    ascii = ascii + chars[i];
+                }
+                e.setAscii(ascii);
             }
-            e.setAscii(ascii);
         }
 
         Optional<ExamStudentCourseDto> minSite = null;
         Optional<ExamStudentCourseDto> maxSite = null;
         if (Objects.nonNull(examStudentList) && examStudentList.size() > 0) {
-            minSite = examStudentList.stream().min(Comparator.comparing(s -> Integer.parseInt(s.getAscii())));
-            maxSite = examStudentList.stream().max(Comparator.comparing(s -> Integer.parseInt(s.getAscii())));
+            minSite = examStudentList.stream().min(Comparator.comparing(s -> Objects.nonNull(s.getAscii()) ? Integer.parseInt(s.getAscii()) : -1));
+            maxSite = examStudentList.stream().max(Comparator.comparing(s -> Objects.nonNull(s.getAscii()) ? Integer.parseInt(s.getAscii()) : -1));
         }
 
         htmlMap.put("minSite", Optional.ofNullable(minSite).map(s -> s.get().getSiteNumber()).orElse(""));