finishing TODO parts

src/CourseRegistrationStarter/Student.java

@@ -21,12 +21,26 @@ public class Student {
     }
 
     public boolean addCourse(Course c) {
+        if(registeredCourses.contains(c))
+            return false;
+        if((c.getCapacity() > 0)){
+            this.registeredCourses.add(c);
+            c.reduceCapacity();
+            return true;
+        }
         // TODO: Register the student in the course if capacity allows
         // Return true if registration was successful, otherwise false
         return false;
     }
 
     public boolean dropCourse(Course c) {
+        for(int i = 0; i < this.registeredCourses.size(); i++){
+            if (this.registeredCourses.get(i) == c){
+                this.registeredCourses.remove(c);
+                c.increaseCapacity();
+                return true;
+            }
+        }
         // TODO: Remove the course from the student's list
         // Restore the course capacity if removal was successful
         // Return true if the course was dropped, otherwise false
@@ -34,6 +48,9 @@ public class Student {
     }
 
     public void showRegisteredCourses() {
+        for(int i = 0; i < registeredCourses.size(); i++){
+            System.out.println(this.registeredCourses.get(i).getCourseName() + ", code: " + this.registeredCourses.get(i).getCourseCode());
+        }
         // TODO: Print all registered courses
     }
 }