Creating special Array

Question

Hi, this is my first post here.
I have been using Java for a few classes at Texas A&M and always seem to get stuck on the same and simplest steps in my programs.
I have a program where input is taken from a file about students. Then information about students is assigned, and by user choices either sorted, displayed , searched and so on.
I need to create an Array of students. so far the class layout of my code is this
class Course{
//set and get methods of grades and other information
class Student{
//set and get of student name and ID
class groupOfStudents{
//display information, read input file and keyboard input
public Testing{
main()
I have to create an array of students and do things like
for(int i = 0; i < MAXQUIZ; i++){
student[1].setQuiz(i, Integer.parseInt(currentLine[3 + i]));
there would be a higher for loop to go through all students, and the currentLine array is readLine().split(" ").
I tried like Course[] student = new Course[numberOfStudents]; and other things of that sort, I bet this is a very simple idea but for some reason an array of non-primitive data types is hard for me because when I use new ClassName all I can see being run is the class constructor.
Any help appreciated thanks :)
null

Answer 1

What I need is an array that is sort of like
Student students[] = new Student[];
I need an array of students with size
numberOfStudents. You're almost there:
Student students[] = new Student[numberOfStudents];
Then for each student I will take
the file input and call set functions for course
information and student information.Well, I'd strongly avoid putting course information into objects that represent students. Rather, create course objects, and put pointers in your student objects to the course objects. Course details would go in course objects. The student class would have something like this in it:
private Course[] courses;
My main question really is how do you create an array
of a non primative data type? Basically the above.
How do you call on a
class and create an array of that class...I've been
doing it, and so far it seems to "work" but it tells
me it can not see the methods in that class. for
instance i'll tell the program...
student[ i ].setQuiz(0, 100); and it tells me can not
find method setQuiz(int, int) in class Course or
Student, and what not and then I tried using extends
(not very good with extends and interface usage).
The method is there, correct spelling, correct type
and number of arguments.Err..my guess is that you're not actually allocating the Student and Course objects, and you're getting NullPointerExceptions and that's confusing you. When you create an array of an object type, the values of the array are initially all null. You have to instantiate them yourself, like this:
Student students = new Student[numberOfStudents];
for(int i = 0; i < numberOfStudents; i++) {
    students[i] = new Student();
}Except for one thing. It's generally a bad idea to create empty objects like that (new Student() without student info in them) and I'm guessing that you really don't know the number of students anyway until you read the file. So a better approach is usually to use a java.util.Collection subclass rather than an array, and then to add to it while you read the data file and create the Student objects on the fly, using data you read from the file.
If this isn't your problem...then please post what you're trying to do (as short and simple as possible) and also the compiler error messages if it won't compile, or the stack traces if it will compile but not run. Wrap the code in [code][/code] tags when you post it.