"Alternatively, we could make our design a bit more flexible by allowing the construction of a Student instance without having to provide a course schedule. Instead, we could add a method that allowed the outside code to add a course to the schedule. Something like the following.\n\npublic void addCourse(Course c) {\n\nthis.schedule.add(c);\n\n}\n\nThis adds some flexibility to our object, but removes the immutability property. Design is always a balance and compromise between competing considerations."