now if the user tries to add an exam to a student that clashes with t…

…he student's lessons, the exam is still added but a warning message is shown

src/main/java/seedu/address/logic/commands/exam/CreateExamCommand.java

@@ -70,6 +70,7 @@ public CreateExamCommand(List<String> names, NamePredicate predicate, String exa
 
     @Override
     public CommandResult execute(Model model) throws CommandException {
+        StringBuilder lessonClashMessage = new StringBuilder("\n");
         requireNonNull(model);
         model.updateFilteredStudentList(PREDICATE_SHOW_ALL_STUDENTS);
 
@@ -105,6 +106,10 @@ public CommandResult execute(Model model) throws CommandException {
 
         try {
             for (Student student : studentList) {
+                if (student.hasLessonAtSameTime(exam)) {
+                    lessonClashMessage.append("*******WARNING*******\n").append(student.getName().fullName)
+                        .append(" has a lesson at the same time as the exam\n Consider rescheduling clashing lesson");
+                }
                 student.addExam(exam);
             }
         } catch (Exception e) {
@@ -118,7 +123,7 @@ public CommandResult execute(Model model) throws CommandException {
         }
 
         return new CommandResult(
-                String.format(Messages.MESSAGE_EXAM_ADDED_SUCCESS, exam, sb));
+                String.format(Messages.MESSAGE_EXAM_ADDED_SUCCESS, exam, sb) + lessonClashMessage);
     }
 
     @Override

src/main/java/seedu/address/model/student/Student.java

@@ -420,6 +420,20 @@ public void addExam(Exam exam) throws DuplicateEntryException, ConflictingExamsE
         this.examList.add(exam);
     }
 
+    /**
+     * Returns true if the exam's time clashes with any lesson's time.
+     * @param exam Exam to be checked
+     * @return boolean
+     */
+    public boolean hasLessonAtSameTime(Exam exam) {
+        for (Lesson lesson : lessonsList) {
+            if (exam.getStartTime().isBefore(lesson.getEndTime()) && exam.getEndTime().isAfter(lesson.getStartTime())) {
+                return true;
+            }
+        }
+        return false;
+    }
+
     /**
      * Returns an exam from the exam list.
      *

src/main/java/seedu/address/model/student/exceptions/ConflictingExamsException.java

@@ -6,6 +6,6 @@
  */
 public class ConflictingExamsException extends RuntimeException {
     public ConflictingExamsException() {
-        super("The exam clashes with another exam");
+        super("The exam clashes with another exam/lesson");
     }
 }