Question

I’m not getting any errors but I couldn’t add Course

    //in my Course class i use equals method to check whether they are the sam
    public boolean equals (Course other){
    Course c = (Course) other;
    if(c != null){
        if (this.name.equals(c.name) && this.instructor.equals(c.instructor) && this.numberOfSection == (c.numberOfSection) && this.year == (c.year))
            return true;
        else
            return false;   
        }
    else 
        return false;
}

//in my CourseCatalog class i use the equals method in Course and if they are not same 
// i add the course to the catalog
public void addCourse (Course other) {
    if(other != null){
        if( !other.equals(course1) && !other.equals(course2) && !other.equals(course3) && !other.equals(course4))
        {
            if (noOfCourse == 0){
                course1 = new Course(other);
                noOfCourse ++;
            }
            if (noOfCourse == 1){
                course2 = new Course(other);
                noOfCourse ++;
            }
            if (noOfCourse == 2){
                course3 = new Course(other);
                noOfCourse ++;
            }
            if(noOfCourse == 3){
                course4 = new Course(other);
                noOfCourse ++;
            }   
        }
    }
}

            //the following code is what i do in the tester class 
            CourseCatalog myCourseCatalog  = new CourseCatalog();
    Course course1 = new Course();
    course1.setName("Math101");
    course1.setInstructor("Jack Smith");
    course1.setYear(2007);
    course1.setNumberOfSection(3);
    myCourseCatalog.addCourse(course1);

            // i add a different course 
    Course course2 = new Course("Cs101", "David Brown", 2003 ,3);
    myCourseCatalog.addCourse(course2);
    Course copyCourse = new Course(course2);
    myCourseCatalog.addCourse(copyCourse);

However the program prints out in this way;

Name: Math101
Instructor: Jack Smith
Year: 2007
Number Of Sections: 3Name: Math101
Instructor: Jack Smith
Year: 2007
Number Of Sections: 3Name: Math101
Instructor: Jack Smith
Year: 2007
Number Of Sections: 3Name: Math101
Instructor: Jack Smith
Year: 2007
Number Of Sections: 3

So that means i cannot addcourse why? I’m a new student in java so I’d appreciate any help.

Answer 1

Wow this is a beauty…

You are using a chain of if-else which makes sure that all the if are true and gets executed. In first if you check for noOfCourse == 0 and then increment it; in the next one you check for noOfCourse==1 which will be true due to the increment.

So when you call you method addCourse first time all courses are already set.

Please Replace

if (noOfCourse == 0){
    course1 = new Course(other);
    noOfCourse ++;
}
if (noOfCourse == 1){
    course2 = new Course(other);
    noOfCourse ++;
}
if (noOfCourse == 2){
    course3 = new Course(other);
    noOfCourse ++;
}
if(noOfCourse == 3){
    course4 = new Course(other);
    noOfCourse ++;
}   

with

if (noOfCourse == 0){
    course1 = new Course(other);
    noOfCourse ++;
} else if (noOfCourse == 1){
    course2 = new Course(other);
    noOfCourse ++;
} else if (noOfCourse == 2){
    course3 = new Course(other);
    noOfCourse ++;
} else if(noOfCourse == 3){
    course4 = new Course(other);
    noOfCourse ++;
}