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Thread: ArrayList as a parameter

  1. #1
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    Default ArrayList as a parameter

    I have five classes all together: Instructor, Student, Course, Section, and Testing.

    In the section class, I have this:

    public class Section {
        private Course course;
        private Instructor instructor;
        private ArrayList<Student> students;
     
        public Section() {
            super();
        }
     
        public Section(Course course) {
     
        }
     
        public Section(Course course, Instructor instructor) {
     
        }
     
        public Section(Course course, Instructor instructor, ArrayList<Student> students) {
     
        }
          // getters and setters
     
        public void setCourse(Course course)
          {
            this.course = course;
          }
     
        public Course getCourse()
          {
            return course;
          }
     
        public void setInstructor(Instructor instructor)
          {
            this.instructor = instructor;
          }
     
        public Instructor getInstructor()
          {
            return instructor;
          }
     
        public void setStudents(ArrayList<Student> students)
          {
            this.students = students;
          }
     
        public ArrayList<Student> getStudents()
          {
            return students;
          }
     
        public void addStudent(Student student)
          {
            students.add(student);  // add a student to the section roster
          }  
        }
    In the main method, I want to create a Section object by accessing this constructor from the Section class:


    public Section(Course course, Instructor instructor, ArrayList<Student> students) {
     
    }

    So I started with:


    public class Testing01 {
        public static void main (String [] args) throws IOException {
     
            Section sec = new Section("Java Programming", "George Jones", /* ArrayList variable here*/); {
     
    }
    }
    }

    I would like the constructor to create the ArrayList, but I can not figure out how to code the parameter. It's not in my reading and I have scoured the Internet for the answer with no results. I really want to comprehend this, so can anyone walk me through this? I would be most appreciative.


  2. #2
    Super Moderator Norm's Avatar
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    Default Re: ArrayList as a parameter

    I would like the constructor to create the ArrayList, but I can not figure out how to code the parameter.
    What class is the constructor in? The Testing01 class does not have a constructor.
    What parameter does the constructor need to have to create the ArrayList?


    Are you asking how to pass a variable to a constructor? Put the name inside the ()s
    TheClass tc = new TheClass(theVariable);
    If you don't understand my answer, don't ignore it, ask a question.

  3. #3
    Super Moderator helloworld922's Avatar
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    Default Re: ArrayList as a parameter

    Creating an ArrayList isn't much different from creating any other object (you're already creating a Section object). Just pick a constructor and call new Constructor(params). Available ArrayList constructors: JavaDoc - ArrayList.


    ex. ArrayList constructor with no parameters
    new ArrayList<Student>()

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    Default Re: ArrayList as a parameter

    Quote Originally Posted by Norm View Post
    What class is the constructor in? The Testing01 class does not have a constructor.
    What parameter does the constructor need to have to create the ArrayList?


    Are you asking how to pass a variable to a constructor? Put the name inside the ()s
    TheClass tc = new TheClass(theVariable);
    I might be using the wrong words. I have the constructor in the Section class:

    public Section(Course course, Instructor instructor, ArrayList<Student> students) {
     
        }

    Am I missing information in the constructor? Is there supposed to be information in between the brackets?

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    Default Re: ArrayList as a parameter

    Quote Originally Posted by helloworld922 View Post
    Creating an ArrayList isn't much different from creating any other object (you're already creating a Section object). Just pick a constructor and call new Constructor(params). Available ArrayList constructors: JavaDoc - ArrayList.


    ex. ArrayList constructor with no parameters
    new ArrayList<Student>()
    Am I not able to use the constructor in the Section class to create the ArrayList variable?

  6. #6
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    Default Re: ArrayList as a parameter

    The Section class constructor creates a Section class object. To create an ArrayList object you need to use an ArrayList constructor.

    The section class constructor takes as a parameter an ArrayList object, which must be constructed using an ArrayList constructor.

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    Default Re: ArrayList as a parameter

    This thread has been cross posted here:

    http://www.java-forums.org/new-java/63536-arraylist-parameter.html

    Although cross posting is allowed, for everyone's benefit, please read:

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  8. #8
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    Default Re: ArrayList as a parameter

    The only reason I cross-posted is because no one answered on the other board. I waited for two days.

    The really horrible fact about this entire thing is that I had finished this, and it was working. Apparently, though, I was told that I did it the hard way and given some advice to change it. Now I am really confused and frustrated.

    I do apologize.
    Last edited by mysdyva; October 5th, 2012 at 03:00 PM.

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