对象从hashmap返回null

Question

Hi I'm working on a Uni assignment and I currently have a class called Program that stores a hashmap called courses .

inside the Program class I can easily return objects from the Hashmap but when I try to retrieve a Course object from the Hashmap in another class University it always returns null .

a snippet of my code:

Program Class

private Map <String, Course> courses = new HashMap<String, Course>();

public void addCourse(Course newCourse) throws ProgramException {
        setCode(newCourse.getCode());
        courses.put(newCourse.getCode(), newCourse);    
    }

    public Course getCourse(String courseID){
        setCode(courseID);
        return courses.get(courseID);
    }

University Class

    public void enrollIntoCourse(String courseID) {
            studentKey = student.getFullName();

            course = program.getCourse(courseID);

// print out Course Object to check. But it = null!!
            System.out.println(course);

            enrolled.put(studentKey, course);

        }

Basically I am trying to get a Course Object from the courses Hashmap to store in another Hashmap that holds Course Objects but with a different key.

Answer 1

I would check that you have properly initialised program and have added courses to it. If you are confident that you've done that, could you show us the code that does so?