complete Bonus methods

src/CourseRegistrationStarter/RegistrationSystem.java

@@ -9,7 +9,12 @@ public class RegistrationSystem {
     }
 
     public void addCourseToSystem(Course c) {
-        courses.add(c);
+        if (courses.contains(c)) {
+            return;
+        }
+        else {
+            courses.add(c);
+        }
     }
 
     public Course findCourseByCode(String code) {
@@ -26,4 +31,12 @@ public class RegistrationSystem {
             System.out.println(c);
         }
     }
+    public Course findCourseByName(String name) {
+        for (Course c : courses) {
+            if (c.getCourseName().equals(name)) {
+                return c;
+            }
+        }
+        return null;
+    }
 }

src/CourseRegistrationStarter/Student.java

@@ -21,10 +21,12 @@ public class Student {
     }
 
     public boolean addCourse(Course c) {
-        if (c.getCapacity() > 0 ) {
-            registeredCourses.add(c);
-            c.reduceCapacity();
-            return true;
+        if (registeredCourses.size() <= 3) {
+            if (c.getCapacity() > 0) {
+                registeredCourses.add(c);
+                c.reduceCapacity();
+                return true;
+            }
         }
         return false;
     }