package studentDB;
/**
 *	Maintains a list of students.  Students may be entered
 *	into the list and retrieved from the list.
 */
public class StudentListImpl extends ListImpl implements StudentList {
    /**
     *	Returns the student at position n.  Indexing is
     *  zero-based, so it must hold that 0<=n<numElements.
     */
    public Student get (int n) {
	return (Student) getElement (n);
    }

    /**
     *	Returns the first student in the list.  The list may not
     *  be empty.
     *	@return The first student in the list.
     */
    public Student first() {
	return (Student)firstElement();
    }
    
    /**
     *  Returns the list of students following the first student.
     *	The list may not be empty.
     *	@return The list of students following the first element.
     */
    public StudentList rest() {
	return (StudentList)restElements();
    }

    /**
     *	Adds the given student to the end of the list.
     *	If the student is already in the list, has no effect.
     *	@param newStudent The element being added
     */
    public void add (Student newStudent) {
	// If the student is already in the list, has no effect.
	// Otherwise, add the element to the rest of the list.
	if (!inList(newStudent)) {
	    addElement (newStudent, new StudentListImpl());
	}
    }
}